volinfo: avoid exit on errors

Instead of exiting on errors, try to carry on.

Reviewed-on: http://gerrit.openafs.org/4736
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 59a1c40efbd3326a210776a0253f4f6c656a65ee)

Change-Id: If5f461ac4c1d35ae27336eeab844e6706fcd5bbe
Reviewed-on: http://gerrit.openafs.org/11254
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: Stephan Wiesand <stephan.wiesand@desy.de>