vos: cross-device link error message

vos: cross-device link error message

Print a better diagnostic message for cross-device link errors, which
happens when a clone volume is not in the same partition as the
parent read-write volume.

Reviewed-on: http://gerrit.openafs.org/10850
Reviewed-by: D Brashear <shadow@your-file-system.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit da1597d74a0f56e35a156ec27df231f965934910)

Change-Id: I30cb0e87612732bfbce2c001831324d1a9e54409
Reviewed-on: http://gerrit.openafs.org/11587
Reviewed-by: Daria Phoebe Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>