Remove race for starting container devices.

Remove race for starting container devices.

This moves the lock handling out of Incremental_container() and relies
on the caller holding the lock. This prevents conflict with a
follow-on mdadm comment which may try and launch the device in
parallel.

This involves replacing a call to "Incremental" with an
unrolled version with just the case that calls Incremental_container
and so needs a call to ->load_container.

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