Add storage policy support to object updates

The object server will now send its storage policy index to the
container server synchronously and asynchronously (via async_pending).

Each storage policy gets its own async_pending directory under
/srv/node/$disk/objects-$N, so there's no need to change the on-disk
pickle format; the policy index comes from the async_pending's
filename. This avoids any hassle on upgrade. (Recall that policy 0's
objects live in /srv/node/$disk/objects, not objects-0.)

Also clean up a couple little things in the object updater. Now it
won't abort processing when it encounters a file (not directory) named
"async_pending-\d+", and it won't process updates in a directory that
does not correspond to a storage policy.

That is, if you have policies 1, 2, and 3, but there's a directory on
your disk named "async_pending-5", the updater will now skip over that
entirely. It won't even bother doing directory listings at all. This
is a good idea, believe it or not, because there's nothing good that
the container server can do with an update from some unknown storage
policy. It can't update the listing, it can't move the object if it's
misplaced... all it can do is ignore the request, so it's better to
just not send it in the first place. Plus, if this is due to a
misconfiguration on one storage node, then the updates will get
processed once the configuration is fixed.

Change-Id: I07c730bebaee068f75024fa9c2fa9e11e295d9bd
Add Storage Policy Support to the Auditor

This patch makes the object auditor policy-aware, so it'll audit
objects in any storage policy.

Change-Id: I94e3a7937d9814b9ecef6ca35371e245a43513d3
Add storage policy support for the Replicator

This makes it so that objects stored in all policies get replicated
properly. This is only for rsync replication, not ssync.

Change-Id: Ifdb4624841f35953ba80189e669d3ef15d5563fd
Add Storage Policy Support to ssync

This patch makes ssync policy aware so that clusters using storage
policies and ssync replication will replicate objects in all policies.

Change-Id: I64879077676d764c6330e03734fc6665bb26f552