python-common/deployment: add a cluster public ip spec for smb

python-common/deployment: add a cluster public ip spec for smb

This spec can be used to define one or more public addresses that will
be automatically assigned to hosts by CTDB. The address can be specified
in the "interface" form - an address plus prefix length.  Optionally,
networks to bind to can be specified. The network value will be
converted to a network device name later by cephadm.

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