Windows: btree enumeration bulk stats

Each of the btree enumeration bulk stat operations include the
directory object in the bulk stat list.  If the only object in the
list is the directory object, do not perform the bulk stat rpc as
it just wastes time.  All of the required objects are already cached
with current callbacks.

Reviewed-on: http://gerrit.openafs.org/9675
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit b518ffc0da37d38f05fa1d35852500784caefba6)

Change-Id: Ic8fe9f6d579fc507252a720012937a0bfa943e31
Reviewed-on: http://gerrit.openafs.org/9714
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Windows: cache readonly volume size information

Cache the volume size information for .readonly volumes which can
be reset when the volume callback is broken.  This reduces the number
of RXAFS_GetVolumeStatus RPC calls issues on .readonly volumes.

Reviewed-on: http://gerrit.openafs.org/9681
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 50faf84b4b46b337cd576f4bcaceed423d63544b)

Change-Id: I4a28ed8dd842f1eee81c46d9f66622c695417989
Reviewed-on: http://gerrit.openafs.org/9715
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>