Add server group limits in test_absLimits_get

Limits about server groups are missing in test_absLimits_get,
see
http://developer.openstack.org/api-ref/compute/?expanded=
show-rate-and-absolute-limits-detail#show-rate-and-absolute-limits

This is to add missing limit items about server group.

Change-Id: If7f62293daa82cdca848d141216dd75386d452ed
1 file changed