Don't force-close for dust HTLCs

[TheBlueMatt]

We currently do, but maybe we should consider not doing that? If we FC for dust we're guaranteed to lose the HTLC anyway, though its a bit weird not to given we'll just sit around with dust in our channel we can't do anything about?

[TheBlueMatt]

Hmm, so we can only do this for sent HTLCs - for forwarded HTLCs if we don't force-close the outbound edge we'll end up just getting the inbound edge channel force-closed. For outbound HTLCs its probably worth force-closing as well - we'd really like to get some kind of HTLC resolution at some point, we can't just let it hang out forever.

[TheBlueMatt]

I guess what I must have been thinking was that we actually do fail the inbound edge of an HTLC back/consider the payment failed, but decline to actually FC. When we communicate with the peer next we give them a chance to fail the HTLC, if they dont (ie they try to claim it) we just FC, if they do we managed to save ourselves an FC.

Still, its a bunch of work and hopefully the "holds HTLC forever" issues are mostly solved by lnd 16.3