Windows: cm_ShutdownSCache corrections

Windows: cm_ShutdownSCache corrections

Obtain cm_scache.dirlock, cm_scache.rw and cm_scacheLock
in the correct order.

Do not release cm_scache.rw when it is not held.

Since the cm_scacheLock is being dropped, preserve the value
of scp->allNextp prior to dropping the lock.

Change-Id: I025a8d76f3f7b94ae00bfd4e000750a90d38b343
Reviewed-on: http://gerrit.openafs.org/5279
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>