Windows: Avoid bottleneck on VolumeLock

Windows: Avoid bottleneck on VolumeLock

The VolumeLock resource was obtained during each AFSParseName()
and held across a wide range of operations including volume
info queries, renames, and extent requests.  These operations can
take a long time to complete and as long as the VolumeLock was
held exclusively there could only be one operation in flight at
a time on a given volume.  This significantly reduced the parallelism
of operations.

The VolumeLock was not required in almost all cases.  This patchset
adjusts the use of the VolumeLock and avoids the bottleneck.

Change-Id: I9d60fe41d157b9e315aeaa15feee8d1e0d4ded4c
Reviewed-on: http://gerrit.openafs.org/6420
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>