DDF: fix bug in compare_super_ddf

Fix bug in previous patch
"DDF: compare_super_ddf: merge local info of other superblock"

Just discovered this bug in my last patch set - unfortunately, just after
you committed it.

Signed-off-by: Martin Wilck <mwilck@arcor.de>
Signed-off-by: NeilBrown <neilb@suse.de>
mdmon: Add missing option documentation to --help output

Document that -a is equivalent to --all, as well as --foreground / -F

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>