Drop the during-reorg channel closure behavior

[TheBlueMatt]

Currently, if we see a block disconnect which reduces our funding transaction confirmation count but doesn't make it 0, and we hit min_confs / 2, we close the channel. There is no reason to think a partial reorg indicates future reorg potential any more than steady-state, plus this risks needless channel closure. We should completely drop this behavior and only force-close if the confirmations hits 0. See-also #838 (comment)

[TheBlueMatt]

#1461 improved this somewhat but #1401 makes it even worse.