Adapt keystone_endpoint for new upstream modules

New openstack modules (v4.0.0) use "${region}/${name}" as
"keystone_endpoint" resource name which is incompatible with old
"keystone" module. From the other hand, new upstream "keystone"
module (v4.0.0) is not compatible with old openstack modules.

This is a temporary workaround to support both old-style and new
"keystone_endpoint" names. It will allow us to use new modules
along with old ones during upstream synchronization process.

This workaround will be removed when we update "keystone" module
to the upstream 4.0.0 version.

Change-Id: Ib5c232599273f93b7806413316d35af176a21bb0
Implements: blueprint merge-openstack-puppet-modules
Merge "Adapt keystone_endpoint for new upstream modules"