osd/OSDMap: implement propapage_snaps_to_tiers()

Tier pools mirror the base pool's snapshot metadata.

Signed-off-by: Sage Weil <sage@inktank.com>
mon/OSDMonitor: propagate snap updates to tier pools on update

For any pg_pool_t update, verify that any changes to the pool snapshot
metadata are propagated to the tiers.

Signed-off-by: Sage Weil <sage@inktank.com>
ceph_test_rados: check existence on is_dirty completion

Signed-off-by: Sage Weil <sage@inktank.com>
osd/ReplicatedPG: clear whiteout on successful copy-from

Signed-off-by: Sage Weil <sage@inktank.com>
ceph_test_rados: update in-memory user_version on RemoveAttrsOp

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