Add a  negative test for security_group api

Currently,test_security_groups_negative.py only prevent to create
a security_group named "default",but sometimes,
user create a security_group named "test-123",
and then change the name to "default",
so we should add negative test as below.

Change-Id: Ie34b854267fefe56eef1f40a1446e73676100bf3
1 file changed