Windows: permit offline volume check to be disabled

Windows: permit offline volume check to be disabled

Setting the registry value to 0 can now be used as a
method of disabling the offline volume check.

Reviewed-on: http://gerrit.openafs.org/5370
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 19a5b5e67c65f0a9109b0fb5410b5ba74ad85b41)

Change-Id: I50dfa3c5387ba8a1cbdd3ca80f9e8dc03e92c404
Reviewed-on: http://gerrit.openafs.org/6036
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>