Windows: Do not execute tasks on deleted files

Windows: Do not execute tasks on deleted files

If a cm_BkgDaemon thread finds a queued request whose cm_scache_t
has the CM_SCACHEFLAG_DELETED flag set, do not execute the request
and fail it immediately with CM_ERROR_BADFD.  Any attempt to execute
the request will fail with VNOVNODE from the file server.

Reviewed-on: http://gerrit.openafs.org/5120
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from afc3ded56795d30e4e0f38d11f8302568943c49b)

Change-Id: I92610c215d7d44ceb1894bb3ab7784534a66e452
Reviewed-on: http://gerrit.openafs.org/5146
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>