More fixes for the Ceph docker images url parsing

More fixes for the Ceph docker images url parsing

Existing code was still failing the following scenario:

  http://192.168.24.1:8787/ceph/rhceph-2-rhel7:latest

Now this has been tested with the following variations:

  http://192.168.24.1:8787/ceph/rhceph-2-rhel7:latest
  http://192.168.24.1:8787/rhceph-2-rhel7:latest
  192.168.24.1:8787/ceph/rhceph-2-rhel7:latest
  192.168.24.1:8787/rhceph-2-rhel7:latest
  192.168.24.1/ceph/daemon:latest

And then the same list without the custom registry host.

Change-Id: Ifc871de8c2678f6a6fc5d234bfb62e8273c1b0b7