vlserver: Remove 'register' argument

vlserver: Remove 'register' argument

Commit 4a531cb7 (death to register) removed the 'register' declaration
from variables/arguments. But commit 3bf03502 (vlserver: Add a struct
for trans-specific data) accidentally added one back in at around the
same time, probably due to a rebase/merge mistake.

Take the 'register' declaration back out.

Change-Id: I73f206a57ab6b97195771e39556d2b0064be4cf3
Reviewed-on: https://gerrit.openafs.org/13346
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>