If no port number was provided for a storage pool libvirt defaults to
port 6789; however, librbd/librados already default to 6789 when no port
number is provided.

In the future Ceph will switch to a new port for the Ceph monitors since
port 6789 is already assigned to a different application by IANA.

Port 6789 is assigned to SMC-HTTPS and Ceph now has port 3300 assigned as
the 'Ceph monitor' port.

In this case it is the best solution to not hardcode any port number into
libvirt and let librados handle the connection.

Only if a user specifies a different port number we pass it down to librados,
otherwise we leave it blank.
Signed-off-by: NWido den Hollander <wido@widodh.nl>

merge