Recently, the builds of `ceph/ceph` image moved to quay.io, see
https://github.com/ceph/ceph-build/pull/1883 for more details.
Current images will remain but new builds will happen on quay.io only.
This means that tags such as `v14.2`, `v15.2`,`v16.2` will need to
switch to quay.io to get updates.
Signed-off-by: Sébastien Han <seb@redhat.com>