Windows: cm_ConnByServer hold userp->mx only while necessary

Windows: cm_ConnByServer hold userp->mx only while necessary

The cm_userp_t does not need to be locked while the cm_conn_t
force new connection processing is taking place.

Reviewed-on: http://gerrit.openafs.org/7718
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 5b9e9265a0df707e9fb79842ab5aa94b59b8e88e)

Change-Id: I0fb0f5b7ede676b4513e33fa664e66cafed18e01
Reviewed-on: http://gerrit.openafs.org/8640
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>