mdadm: set journal_clean after scanning all disks

mdadm: set journal_clean after scanning all disks

Summary:
In Incremental.c:count_active(), max_events is tracked to show to
which devices are up to date. If a device has events==max_events+1,
getinfo_super() is called to reload the superblock from this
device. getinfo_super1() blindly set journal_clean to 0, which is
wrong.

This patch fixes this by tracking max_journal_events for all the
disks. After scanning all disks, journal_clean is set if
max_journal_events >= max_events-1.

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>