The rhel-common element has a script that uses subscription-manager
to register an instance of RHEL with the customer portal or Satellite.
If os-refresh-config runs this script more than once,
subscription-manager returns a non-zero value causing os-refresh-config
to fail. Adding --force to the subscription-manager calls doesn't
properly unregister the image from Satellite and the result is multiple
content host registrations. This patch changes the registration to only
run once.
Change-Id: If372e7f59bbdc77e2b233024c1342f005004f2e5
c9af576e79