test_volume_client: add positive test for ceph_volume_client method

test_volume_client: add positive test for ceph_volume_client method

ceph_volume_client.py's put_object_versioned() has only one test. Since
this only test is a negative test it may fail to assure that
put_object_versioned() works as expected with positive inputs even when
it completes successfully. Therefore, write a positive test for better
coverage.

Also, make sure the new test is both python 2 and python3 compatible.

Signed-off-by: Rishabh Dave <ridave@redhat.com>