ceph_test_rados: fix update_object_full

Update at current snap, not the last snap we did an update.

Broken this this was introduced in 996af2d8fd8e60bcdce8e9408249b974521de24e

Signed-off-by: Sage Weil <sage@inktank.com>
debug
ceph_test_rados: improve debug output

Signed-off-by: Sage Weil <sage@inktank.com>