Windows: clear ASYNCSTORING flag in scache recycle

If the scache has been recycled the ASYNCSTORING flag cannot
be accurrate.  Clear it.

Change-Id: Ie5a5a19bf1818e36f6274ba24ddeaf5f4b835ff4
Reviewed-on: http://gerrit.openafs.org/8970
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>