Windows FindACLCache must hold scp write locked

Windows FindACLCache must hold scp write locked

In the SMB modules, calls to cm_FindACLCache() were not
holding the cm_scache_t rwlock writed locked as required.

Reviewed-on: http://gerrit.openafs.org/7015
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>
(cherry picked from commit 0896602f6e7c409990fcae40dd54f84260312472)

Change-Id: I29313f479ae2487a615b065d601ee5d0ef994ccf
Reviewed-on: http://gerrit.openafs.org/8619
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>