Unneeded identity reg done for api-cfn

When the heat cloud formation (api-cfn recipe) is not needed and
not used, the identity recipe still creates service and endpoint
identity registrations for it. I added a check to see if the
api-cfn recipe is in the run_list, suggestions welcome for better
ways to approach this.

Change-Id: I5f326a66f005f0553aecd8cea798a224d76f57c4
Closes-bug: 1279577