bcrypt keys are in the rxkad list, not the rxgk list

Fix the presumed typo in the loop intended to skip them.

Change-Id: I863fb12792b82d528938ad0598aa626880f11a41
Reviewed-on: http://gerrit.openafs.org/10947
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>