ceph_test_rados: update in-memory user_version on RemoveAttrsOp

Signed-off-by: Sage Weil <sage@inktank.com>
ceph_test_rados_api_tier: more grace for HitSetTrim

Saw this test fail due to ill-timed thrashing:

 /a/teuthology-2013-12-20_23:00:02-rados-master-testing-basic-plana/10941

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