switching to decorators.idempotent_id

Now most testcases have switched to using decorators.idempotent_id,
except two testcases,  this is to fix them.

Change-Id: I0e57be7c654417a6f2687f141ae790084436c800
diff --git a/tempest/api/compute/flavors/test_flavors_negative.py b/tempest/api/compute/flavors/test_flavors_negative.py
index a70c0a9..b313f44 100644
--- a/tempest/api/compute/flavors/test_flavors_negative.py
+++ b/tempest/api/compute/flavors/test_flavors_negative.py
@@ -21,6 +21,7 @@
 from tempest.common import image as common_image
 from tempest.common.utils import data_utils
 from tempest import config
+from tempest.lib import decorators
 from tempest.lib import exceptions as lib_exc
 from tempest import test
 
@@ -43,7 +44,7 @@
 
     @test.attr(type=['negative'])
     @test.services('image')
-    @test.idempotent_id('90f0d93a-91c1-450c-91e6-07d18172cefe')
+    @decorators.idempotent_id('90f0d93a-91c1-450c-91e6-07d18172cefe')
     def test_boot_with_low_ram(self):
         """Try boot a vm with lower than min ram
 
diff --git a/tempest/api/compute/security_groups/test_security_groups.py b/tempest/api/compute/security_groups/test_security_groups.py
index 349bfda..e90a1fc 100644
--- a/tempest/api/compute/security_groups/test_security_groups.py
+++ b/tempest/api/compute/security_groups/test_security_groups.py
@@ -145,7 +145,7 @@
         self.assertEqual(s_new_name, fetched_group['name'])
         self.assertEqual(s_new_des, fetched_group['description'])
 
-    @test.idempotent_id('79517d60-535a-438f-af3d-e6feab1cbea7')
+    @decorators.idempotent_id('79517d60-535a-438f-af3d-e6feab1cbea7')
     @test.services('network')
     def test_list_security_groups_by_server(self):
         # Create a couple security groups that we will use