Give a default reason in *sync-debug

Give a default reason in *sync-debug

If no -reason is given for fssync-debug calls, we currently just
transmit garbage to the fileserver or salvageserver. Instead, give a
default (the *_WHATEVER constant), so we do something consistent.

Reviewed-on: http://gerrit.openafs.org/4115
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 7f31a11d110085ae528d4555d34744c0832008b0)

Change-Id: I27aefea0e891444e006e5d4b5ed43ed9cd492242
Reviewed-on: http://gerrit.openafs.org/5756
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>