btrfs-progs: silence fake fsck

btrfs-progs: silence fake fsck

Harald suggested that we remove the message from the fake fsck.btrfs
that some distros run at boot:

  https://bugzilla.redhat.com/show_bug.cgi?id=1206502

"This output does not add anything, but is a disturbing element of
booting up a system. It's the only message I get, when starting my
system, before gdm is started."

I'm inclined to agree.

This makes the tiniest change to remove the message that's output for an
auto invocation.  My guess is that it was just copied from the xfs
fsck.xfs and that no one actually cares about it.

Signed-off-by: Zach Brown <zab@zabbo.net>
Signed-off-by: David Sterba <dsterba@suse.cz>