ceph-volume-client: allow atomic updates for RADOS objects

ceph-volume-client: allow atomic updates for RADOS objects

put_object_versioned() takes the version of the object and verifies if
the version of the object is the expected one before updating the data
in the object. This verification of version before actually writing
makes put_objcet_version() atomic.

Rest of the changes include adding get_object_and_version() so that
current version of the object can be obtained and modification of
get_object() and put_object() to use get_object_and_version() and
put_object_versioned() respectively.

Fixes: http://tracker.ceph.com/issues/24173
Signed-off-by: Rishabh Dave <ridave@redhat.com>