md/raid1: Avoid raid1 resync getting stuck

md/raid1: Avoid raid1 resync getting stuck

close_sync() needs to set conf->next_resync to a large, but safe value
below MaxSector and use it to determine whether or not to set
start_next_window in wait_barrier()

Solution suggested by Neil Brown.

Reported-by: Nate Dailey <nate.dailey@stratus.com>
Tested-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
(cherry picked from commit e8ff8bf09ff49733534ff3cee91bde030186055f)

Orabug: 28529228

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>