src/afs: Set but unused variables warning fixes

src/afs: Set but unused variables warning fixes

Fix a few simple cases of set but unused variables under src/afs.

Change-Id: I78964b7128590d5db1f2c01dd7157c23966c26a0
Reviewed-on: http://gerrit.openafs.org/4491
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>