update test sec group rules

In Havana, a default security group is
created per tenant. This causes the
security groups part of the test file
to fail b/c it expects only one group
named default, and since the credentials
used are for admin, it winds up seeing
two security groups named default
(from admin and services tenants).

This commit updates the test to create
its own security group to get around
this issue.

Change-Id: Iddf315e732f8e275fc193e00b74dcbda9d73bc25