Windows: reset volume NOEXIST flag

Windows: reset volume NOEXIST flag

In response to fs checkvolumes the NOEXIST flag should be reset.

It should also be reset if the volume location update fails
because of a commumicaton (or other) error with the VLDB server.
The volume's lastUpdateTime is refreshed on error.

Change-Id: I0bb5e61b9eb8a9613d47a32acda35b79aa71c293
Reviewed-on: http://gerrit.openafs.org/7969
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>