net: openvswitch: fixes potential deadlock in dp cleanup code

The previous patch introduced a deadlock, this patch fixes it by making
sure the work is canceled without holding the global ovs lock. This is
done by moving the reorder processing one layer up to the netns level.

Fixes: eac87c41 ("net: openvswitch: reorder masks array based on usage")
Reported-by:  <syzbot+2c4ff3614695f75ce26c@syzkaller.appspotmail.com>
Reported-by:  <syzbot+bad6507e5db05017b008@syzkaller.appspotmail.com>
Reviewed-by: Paolo <pabeni@redhat.com>
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>