Windows: Do not permit RDR worker threads to quit

Windows: Do not permit RDR worker threads to quit

If the DeviceIoControl from the service's redirector worker threads
fails the thread will terminate.  This is a problem because if all
of the threads quit the afs redirector will end up deadlocking
all requests since there will be no method of delivering them to
the service.  If there is an error log it (if possible), and retry.
Hopefully it will be transient.

Change-Id: I3ce5e338e41fd71c5289fe778789f0300c0b5ecd
Reviewed-on: http://gerrit.openafs.org/7627
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>