Removed un-necessary tests from test servers

* Removed tests to create/update servers using links,
  as these should be handled with different test configs
* Added check to test_create_server_with_admin_password to verify
  the admin user can log in with the provided password

Change-Id: I1761b91284e851b3afd805ff76a318d8b18485be
Merge "Removed un-necessary tests from test servers"