afs: Add a little more info on SLVC loop panic

If we panic due to a perceived infinite loop, log a little more info
about our loop iterations.

Reviewed-on: http://gerrit.openafs.org/8850
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 2f087dc434f62cfa7888434427eaac6803b563ab)

Change-Id: Ie4a02a40fafa88f8b54b05b8a0926f258ae7cf7a
Reviewed-on: http://gerrit.openafs.org/9509
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>