vos: changeaddr refuse to change mh entries without -force

vos: changeaddr refuse to change mh entries without -force

Add a client side check to vos changeaddr -oldaddr -newaddr
to refuse to change multihomed server entries, unless -force
is given.

Reviewed-on: http://gerrit.openafs.org/11638
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 656aaacd01a90f658a5126111af9988fa1854dec)

Change-Id: I4eb7e2b3a2e027b5e1368298a274b0328c8b1343
Reviewed-on: http://gerrit.openafs.org/12087
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>