Fix verify_tempest_config with disabled services

The script silently fails when verifying API versions for services
that are not deployed or configured in the catalog.  This fixes it
by only verifying versions for services that actually exist in
keystone.

Change-Id: Iee3724f8bbbfe767e3c6e0b9ee0f9f818e87f68b
Merge "Fix verify_tempest_config with disabled services"