libadmin: Catch VL_GetNewVolumeId failures

If ubik_VL_GetVolumeId fails in the vos ProcessEntries routine,
report the failure and give up, rather than continuing with a
0 maxVolid

Caught by coverity (#988417)

Reviewed-on: http://gerrit.openafs.org/9268
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 8192554e36272d5ed21007b4c0e3b6c56511457d)

Change-Id: I004386d62dc9d2955a795c4c5952b573ff203784
Reviewed-on: http://gerrit.openafs.org/11010
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>