Windows: mark server reference offline for VOFFLINE

Windows: mark server reference offline for VOFFLINE

cm_Analyze() was not marking the cm_ServerRef_t reference to
a volume instance as srv_offline in response to a VOFFLINE error.
As a result the same volume instance is tried again and again.

Reviewed-on: http://gerrit.openafs.org/8326
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit e59cf940ce1cb2ed72ccf05ce39f73019547d9b1)

Change-Id: Iab79c0b2e0c885a0d9180c000f9cc9574fab11dc
Reviewed-on: http://gerrit.openafs.org/8644
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>