Windows: cleanup redirector pipes

Windows: cleanup redirector pipes

If pipe creation fails, cleanup the mess.

At shutdown, if there are pipes that have not been closed by
Windows, clean them up.

This is just to ensure that at shutdown the reference counts of
cm_scache_t objects in the cache are reset to zero.

Change-Id: I1d738c31faafce445f05adc4884c7711123589e2
Reviewed-on: http://gerrit.openafs.org/7366
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>