windows: pass cm_req_t through background ops

windows: pass cm_req_t through background ops

add cm_req_t object to background daemon operations in order to
permit request source to be propagated to the background daemon.

pass a cm_req_t into buf_SetDirty().

Reviewed-on: http://gerrit.openafs.org/5348
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 722843e2df533e8fcf245f2a3b10ef686992deb2)

Change-Id: I2fbc78cf765c534fc6fc673695634fcf946dca0b
Reviewed-on: http://gerrit.openafs.org/6026
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>