md: Whenassemble the array, consult the superblock of the freshest device

Upon assembling the array, both kernel and mdadm allow the devices to have event
counter difference of 1, and still consider them as up-to-date.
However, a device whose event count is behind by 1, may in fact not be up-to-date,
and array resync with such a device may cause data corruption.
To avoid this, consult the superblock of the freshest device about the status
of a device, whose event counter is behind by 1.

Signed-off-by: Alex Lyakas <alex.lyakas@zadara.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/1702470271-16073-1-git-send-email-alex.lyakas@zadara.com