Incremental - avoid including wayward devices.

Incremental - avoid including wayward devices.

If a devices - typically in a mirrored set - is assembled
independently of the other devices, and then attempted to be brought
back into the set, it could contain inconsistent data.  It should not
be included.

So detect this situation by ensuring that the 'most recent' device is
believed to be active by every other device.  If a device is wayward,
it will only consider fellow wayward devices to be active and will
think all others are failed or missing.

This patches fixes --incremental, --assemble was done in an earlier
patch.

Signed-off-by: NeilBrown <neilb@suse.de>