vldb_check: remove unused functions

Remove the readSIT function, which has been unused
since the IBM days.  Remove the commented out and
unimplemented writeUbikHeader stub.

Reviewed-on: http://gerrit.openafs.org/7613
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 7f646382f633fb83d2054298cd5ce12a7bfa250c)

Change-Id: I706e3728216cecf0d0c12ad3008ff0ae6ddbc553
Reviewed-on: http://gerrit.openafs.org/11159
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>