KEYSTONE_CATALOG_BACKEND is deprecated
KEYSTONE_CATALOG_BACKEND is deprecated

this removes it
see: http://lists.openstack.org/pipermail/openstack-dev/2016-February/086272.htm

Change-Id: Idfbec51799a714433d295d6223d1126cb3a0be36

openstack/aodh,openstack/aodh