vlserver: Add auditing to some more RPC's

A future commit will conditionally restrict access to these RPC's.
Auditing will allow debugging and monitoring of this feature.

Change-Id: Id8a8a1831c82ef967eb6cced1609915d1d6b774f
Reviewed-on: http://gerrit.openafs.org/10939
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>