mgr/cephadm: add filter_host_candidates method to smb service class

mgr/cephadm: add filter_host_candidates method to smb service class

Add a filter_host_candidates method to the smb service class allowing
that class to act as a HostSelector. The HostSelector was added in an
earlier commit to allow classes like this one to make specific host
selections based on unique to that class (or it's spec) criteria.

This method uses the newly added `bind_addrs` field of the smb service
spec to ensure only hosts that meet the desired set of
networks/addresses get used in placement.

Signed-off-by: John Mulligan <jmulligan@redhat.com>