Separate security group rule test for each args

If passing "group_id" argument to "add security group rule" API, the
API ignores "cidr" argument.
In test_security_group_rules_create_with_optional_arguments, both
arguments are specified and that is meaningless.
This patch separates it for each purpose.

This patch removes success code checks from each test because the code
is already checked in the client method create_security_group_rule().

Change-Id: I1af1f37eb2d4b4f182d7ab69bcb0e9c37a356e35
Related-Bug: #1373832
Merge "Separate security group rule test for each args"