Use api_extensions to decide security_group type nova used

Even the system enables neutron, if neutron's security_group
extension is disabled, Nova can still use nova's security_group
by setting security_group_api=nova in nova.conf. So this is to
use neutron's security group only when neutron is enabled and
neutron's security_group extension is enabled.

Change-Id: I713b2fb04400c1b892aec9b09e0ff744db8d8d4e
Closes-Bug: #1583851
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 5125e2b..e6abf28 100644
--- a/tempest/api/compute/security_groups/test_security_groups_negative.py
+++ b/tempest/api/compute/security_groups/test_security_groups_negative.py
@@ -44,9 +44,11 @@
             security_group_id.append(body[i]['id'])
         # Generate a non-existent security group id
         while True:
-            non_exist_id = data_utils.rand_int_id(start=999)
-            if self.neutron_available:
+            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