dafs: remove the salvageserver -datelogs option

dafs: remove the salvageserver -datelogs option

Remove the undocumented -datelogs option from the salavageserver, which
was a carry over from the standalone salvager program, but is not
appropriate for a daemon.

Change-Id: Ia382d6550e0641edcba55a414e00323755487e18
Reviewed-on: http://gerrit.openafs.org/11814
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>