debian: correct ceph-common relationship with older radosgw package

debian: correct ceph-common relationship with older radosgw package

Fixes: https://tracker.ceph.com/issues/36741
9fd30b93f7281fad70b93512f0a25e3465f5b225 moved
/etc/bash_completion.d/radosgw-admin from radosgw to ceph-common. This
means that if you try and install a newer ceph-common over an older
radosgw, there's a conflict, and the install fails:

```
Unpacking ceph-common (12.2.8-1xenial) over (10.2.9-0ubuntu0.16.04.1) ...
dpkg: error processing archive ceph-common_12.2.8-1xenial_amd64.deb (--install):
 trying to overwrite '/etc/bash_completion.d/radosgw-admin', which is also in package radosgw 10.2.9-0ubuntu0.16.04.1
```

Per Debian policy (
https://www.debian.org/doc/debian-policy/ch-relationships.html#overwriting-files-in-other-packages
) the correct way to handle a package taking over a file is for a
versioned Replaces and Breaks.

The change went into 12.0.3, so this commit adds Replaces and Breaks
against radosgw less than that version. It should be backported to
Luminous to avoid issues with upgrades from older versions (Jewel and
Kraken).

Signed-off-by: Matthew Vernon <mv3@sanger.ac.uk>