Link dafssync-debug(8) to fssync-debug(8)

Link dafssync-debug(8) to fssync-debug(8)

The two commands are documented identically for right now, so just link
the dafssync-debug man page to the fssync-debug man page.  Remove the
incorrect statement in the man page that fssync-debug only works with
demand-attach.

FIXES 128166

Change-Id: I812641ad7a345c7f5412c3c97ed1ba393e981639
Reviewed-on: http://gerrit.openafs.org/2836
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 68d074d8aa98e76fb85289c69300d17695b98d0b)
Reviewed-on: http://gerrit.openafs.org/2847
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: Russ Allbery <rra@stanford.edu>