container/build.sh: Use dedicated debug tags

container/build.sh: Use dedicated debug tags

https://github.com/ceph/ceph-build/pull/2497 introduced a debug flavor.
This seems to cause conflicts with the image being pushed to quay as one
of the flavors might override the other.

Tag debug build containers explicitly.
Alternative solution would be to skip debug containers all together.
However. these might be useful for development purposes.

Note, prune-quay might also need to be updated once this is merged.

Signed-off-by: Matan Breizman <mbreizma@redhat.com>