paxos: use MonitorStore::put_bl_sn_map() to commit batches of values
paxos: use MonitorStore::put_bl_sn_map() to commit batches of values

This allows us to (safely) do fsync vs sync optimizations.  The old code
would write values to the final names and then sync(2), but a crash in
between could leave 0-length (non-temporary) files and crash.

Fixes: #1414
Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph