Re-instate security group delete test case

While fixing lp#956366, we realized that it's fine to delete a security
group referenced by an ingress rule of another security group because
the ingress rule gets deleted.

Re-instate the test for this specific case, but test that the ingress
rule gets deleted rather than an exception being thrown.

Change-Id: I81ad16431f5f8f13561dfcb320213366e1e8864e

nova/tests/api/ec2/test_cloud.py

@@ -496,6 +496,25 @@ def test_revoke_security_group_ingress_missing_group_name_or_id(self):
         self.assertRaises(exception.EC2APIError, revoke,
                 self.context, **kwargs)
 
+    def test_delete_security_group_in_use_by_group(self):
+        group1 = self.cloud.create_security_group(self.context, 'testgrp1',
+                                                  "test group 1")
+        group2 = self.cloud.create_security_group(self.context, 'testgrp2',
+                                                  "test group 2")
+        kwargs = {'groups': {'1': {'user_id': u'%s' % self.context.user_id,
+                                   'group_name': u'testgrp2'}},
+                 }
+        self.cloud.authorize_security_group_ingress(self.context,
+                group_name='testgrp1', **kwargs)
+
+        group1 = db.security_group_get_by_name(self.context,
+                                               self.project_id, 'testgrp1')
+        get_rules = db.security_group_rule_get_by_security_group
+
+        self.assertTrue(get_rules(self.context, group1.id))
+        self.cloud.delete_security_group(self.context, 'testgrp2')
+        self.assertFalse(get_rules(self.context, group1.id))
+
     def test_delete_security_group_in_use_by_instance(self):
         """Ensure that a group can not be deleted if in use by an instance."""
         image_uuid = 'cedef40a-ed67-4d10-800e-17455edce175'