pybind/rbd: RBD.create() method's 'old_format' parameter now defaults to False

pybind/rbd: RBD.create() method's 'old_format' parameter now defaults to False

The RBD v1 format has been deprecated for numerous releases and creation of
v1 format images has been disabled since the Mimic release. This fixes
the Python API's image create() method to ensure v2 images are created by
default (and no longer throw an exception that creation of v1 images are
disabled).

Fixes: https://tracker.ceph.com/issues/45504
Signed-off-by: Jason Dillaman <dillaman@redhat.com>
(cherry picked from commit 45349355f4b41c6f9de594ef34a8657230113e6b)