Windows: out of order locks cm_CheckCBExpiration

Windows: out of order locks cm_CheckCBExpiration

The recent refactoring of cm_CheckCBExpiration introduced
a lock ordering error between the cm_scache_t rw lock and the
cm_scacheLock.  This patchset fixes the error by dropping the
cm_scacheLock as each cm_scache_t is being processed.

Reviewed-on: http://gerrit.openafs.org/3773
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 67195401c915b23e092f98c89ab5f5580a9cf3f6)

Change-Id: I14e57ca1b6b2f86bee585bc6fa86bdf0b7d77d44
Reviewed-on: http://gerrit.openafs.org/3872
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>