volinfo: fix false good magic line

Fix false report of good magic/version numbers in volume
header file.

Reviewed-on: http://gerrit.openafs.org/4817
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 36f6eed2b458995ab973102acf74375bf0a66931)

Change-Id: Id5972430ae8e2fe374a854c3c33d2837aac48185
Reviewed-on: http://gerrit.openafs.org/11260
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>