afs: Add a little more info on SLVC loop panic

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.

Change-Id: Ifbb6d613aa482dbc33f7ba13dc959709e1688f15
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>