Block X-Backend* in gatekeeper

By moving the blocking to gatekeeper from the proxy server, we gain
the ability to pass X-Backend headers in via InternalClient while
still keeping real clients from using them.

I wanted this functionality while working on storage policies; I had
an InternalClient and wanted to tell it to use a specific policy index
instead of what the container said, and that seemed like a good time
for an X-Backend header.

Change-Id: I4089e980d3cfca660365c7df799723b1f16ba277
Merge "Block X-Backend* in gatekeeper"
Add Storage Policy Support

The basic idea here is to replace the use of a single object ring in
the Application class with a collection of object rings. The
collection includes not only the Ring object itself but the policy
name assocaited with it, the filename for the .gz and any other
metadata associated with the policy that may be needed. When
containers are created, a policy (thus a specific obj ring) is
selected allowing apps to specify policy at container creation time
and leverage policies simply by using different containers for object
operations.

The policy collection is based off of info in the swift.conf file.
The format of the sections in the .conf file is as follows:

swift.conf format:

    [storage-policy:0]
    name = chicken

    [storage-policy:1]
    name = turkey
    default = yes

With the above format:

- Policy 0 will always be used for access to existing containers
  without the policy specified. The ring name for policy 0 is always
  'object', assuring backwards compatiblity. The parser will always
  create a policy 0 even if not specified

- The policy with 'default=yes' is the one used for new container
  creation. T allows the admin to specify which policy is used without
  forcing the application to add the metadata.

This commit simply introduces storage policies and the loading
thereof; nobody's using it yet. That will follow in subsequent
commits.

Change-Id: Ica05f41ecf3adb3648cc9182f11f1c8c5c678985
Storage policy support for REST API

There are two major pieces in this diff: the container piece and the
object piece.

Objects now have a storage policy index associated with them as well;
this is determined by their filesystem path. Like before, objects in
policy 0 are in /srv/node/$disk/objects; this provides compatibility
on upgrade. (Recall that policy 0 is given to all existing data when a
cluster is upgraded.) Objects in policy 1 are in
/srv/node/$disk/objects-1, objects in policy 2 are in
/srv/node/$disk/objects-2, and so on.

Containers now have a storage policy index associated with them,
stored in the container_stat table. This index is only at container
creation time, and cannot be changed without deleting and recreating
the container. This is because a container's policy index applies to
all its objects, so changing a container's policy index would require
moving large amounts of object data around.  Thus, if it is desired to
change the policy for data in a container, the supported method would
be to create a new container with the desired policy and move the data
over.

This commit does not address replicators, auditors, or updaters except
where method signatures changed. They'll still work if your cluster
has only one storage policy, though.

Change-Id: I983c7fb0cc39df002600586aa990f10d277a4b67
Add Storage Policy Support to list_endpoints

This patch makes list_endpoints policy aware so that the object is
looked up in the right ring and its actual locations returned to the
client.

Change-Id: Ic33f54d806e85c969f65e6feab8ab45b16648975
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
Put X-Timestamp in object 404 responses

This way the container reconciler can tell (sometimes) that an object
was deleted at a certain time.

Change-Id: Idaba3255f4109e5150d6c457f913c600fd8923eb