Windows: Improve logging for StoreMini and cm_BufWrite

Windows: Improve logging for StoreMini and cm_BufWrite

Add trace logging to cm_StoreMini which never had it before.

Improve the logging of cm_BufWrite by adding the trucPos value
which is the new length of the file that is being reported to
the file server.

Remove cm_buf_t data references when cm_BufWrite is performing
operations using rx_Writev and iovec structures.

Reviewed-on: http://gerrit.openafs.org/4924
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 21854e03eb6fe70a70ea5fecde5c4ef8074e28c9)

Change-Id: I3bd5d7d834ddfa11044cf3f44af108f0554096b6
Reviewed-on: http://gerrit.openafs.org/4953
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>