Add generate_random_security_group_id in BaseSecurityGroupsTest

This is to add generate_random_security_group_id in BaseSecurityGroupsTest,
so that all security_group tests can use it.
Besides, currently there are two functions which are used to generate
not_existing_id(_generate_a_non_existent_security_group_id and
not_existing_id), because generally speaking, rand_uuid or rand_int_id
can seldom be same, so we can use the simple way to generate
not_existing_id.

Change-Id: Ib6118c74ac080b3fdd7f1e77ac37f24792793d57
diff --git a/tempest/api/compute/security_groups/base.py b/tempest/api/compute/security_groups/base.py
index f70f6d3..cb18775 100644
--- a/tempest/api/compute/security_groups/base.py
+++ b/tempest/api/compute/security_groups/base.py
@@ -14,6 +14,11 @@
 #    under the License.
 
 from tempest.api.compute import base
+from tempest.common.utils import data_utils
+from tempest import config
+from tempest import test
+
+CONF = config.CONF
 
 
 class BaseSecurityGroupsTest(base.BaseV2ComputeTest):
@@ -23,3 +28,11 @@
         # A network and a subnet will be created for these tests
         cls.set_network_resources(network=True, subnet=True)
         super(BaseSecurityGroupsTest, cls).setup_credentials()
+
+    @staticmethod
+    def generate_random_security_group_id():
+        if (CONF.service_available.neutron and
+            test.is_extension_enabled('security-group', 'network')):
+            return data_utils.rand_uuid()
+        else:
+            return data_utils.rand_int_id(start=999)
diff --git a/tempest/api/compute/security_groups/test_security_group_rules_negative.py b/tempest/api/compute/security_groups/test_security_group_rules_negative.py
index 32b3ea3..78c19ca 100644
--- a/tempest/api/compute/security_groups/test_security_group_rules_negative.py
+++ b/tempest/api/compute/security_groups/test_security_group_rules_negative.py
@@ -15,20 +15,9 @@
 
 from tempest.api.compute.security_groups import base
 from tempest.common.utils import data_utils
-from tempest import config
 from tempest.lib import exceptions as lib_exc
 from tempest import test
 
-CONF = config.CONF
-
-
-def not_existing_id():
-    if (CONF.service_available.neutron and
-        test.is_extension_enabled('security-group', 'network')):
-        return data_utils.rand_uuid()
-    else:
-        return data_utils.rand_int_id(start=999)
-
 
 class SecurityGroupRulesNegativeTestJSON(base.BaseSecurityGroupsTest):
 
@@ -44,7 +33,7 @@
         # Negative test: Creation of Security Group rule should FAIL
         # with non existent Parent group id
         # Adding rules to the non existent Security Group id
-        parent_group_id = not_existing_id()
+        parent_group_id = self.generate_random_security_group_id()
         ip_protocol = 'tcp'
         from_port = 22
         to_port = 22
@@ -179,7 +168,7 @@
     def test_delete_security_group_rule_with_non_existent_id(self):
         # Negative test: Deletion of Security Group rule should be FAIL
         # with non existent id
-        non_existent_rule_id = not_existing_id()
+        non_existent_rule_id = self.generate_random_security_group_id()
         self.assertRaises(lib_exc.NotFound,
                           self.rules_client.delete_security_group_rule,
                           non_existent_rule_id)
diff --git a/tempest/api/compute/security_groups/test_security_groups_negative.py b/tempest/api/compute/security_groups/test_security_groups_negative.py
index e6abf28..bcada1e 100644
--- a/tempest/api/compute/security_groups/test_security_groups_negative.py
+++ b/tempest/api/compute/security_groups/test_security_groups_negative.py
@@ -37,29 +37,13 @@
         super(SecurityGroupsNegativeTestJSON, cls).resource_setup()
         cls.neutron_available = CONF.service_available.neutron
 
-    def _generate_a_non_existent_security_group_id(self):
-        security_group_id = []
-        body = self.client.list_security_groups()['security_groups']
-        for i in range(len(body)):
-            security_group_id.append(body[i]['id'])
-        # Generate a non-existent security group id
-        while True:
-            if (self.neutron_available and
-                test.is_extension_enabled('security-group', 'network')):
-                non_exist_id = data_utils.rand_uuid()
-            else:
-                non_exist_id = data_utils.rand_int_id(start=999)
-            if non_exist_id not in security_group_id:
-                break
-        return non_exist_id
-
     @test.attr(type=['negative'])
     @test.idempotent_id('673eaec1-9b3e-48ed-bdf1-2786c1b9661c')
     @test.services('network')
     def test_security_group_get_nonexistent_group(self):
         # Negative test:Should not be able to GET the details
         # of non-existent Security Group
-        non_exist_id = self._generate_a_non_existent_security_group_id()
+        non_exist_id = self.generate_random_security_group_id()
         self.assertRaises(lib_exc.NotFound, self.client.show_security_group,
                           non_exist_id)
 
@@ -139,7 +123,7 @@
     @test.services('network')
     def test_delete_nonexistent_security_group(self):
         # Negative test:Deletion of a non-existent Security Group should fail
-        non_exist_id = self._generate_a_non_existent_security_group_id()
+        non_exist_id = self.generate_random_security_group_id()
         self.assertRaises(lib_exc.NotFound,
                           self.client.delete_security_group, non_exist_id)
 
@@ -204,7 +188,7 @@
     @test.services('network')
     def test_update_non_existent_security_group(self):
         # Update a non-existent Security Group should Fail
-        non_exist_id = self._generate_a_non_existent_security_group_id()
+        non_exist_id = self.generate_random_security_group_id()
         s_name = data_utils.rand_name('sg')
         s_description = data_utils.rand_name('description')
         self.assertRaises(lib_exc.NotFound,