Windows: RXAFS_BulkStat failures

The RXAFS_BulkStat RPC is quite brain dead. The client requests
status information on up to AFSCBMAX FIDs.  The file server replies
success only if all of the client credentials provide access to
all of the requested FIDs.  If status info cannot be provided
for any one of the FIDs, the error code of the failure is returned
with no context as to which FID failed.

To simplify the logic within the cache manager a new local error
code, CM_ERROR_BULKSTAT_FAILURE is introduced to replace whatever
error was received from the file server.  This error is returned
by cm_TryBulkStat and cm_TryBulkStatRPC.  The caller of either of
those functions should interpret the error to mean that the current
user context cannot be used to perform a bulkstat operation against
the provided cm_scache directory.  Instead, individual RXAFS_FetchStatus
operations must be performed.

This patchset implements such error handling for both the SMB and
RDR interfaces.  This change permits the Windows cache manager to
properly enumerate a directory for which the user only has list
permission and cannot read the status info for files and symlinks.

Change-Id: I8cc47a5cedfd4e7bf0db55efffc5e95be5172e85
Reviewed-on: http://gerrit.openafs.org/9080
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>