autopilot/agent: signal chanOpenFailureUpdates on own channel
autopilot/agent: signal chanOpenFailureUpdates on own channel

We do this to avoid a huge amount of goroutines piling up when autopilot
is trying to open many channels, as they will all block trying to send
the update on the stateUpdates channel. Now we instead send them on a
buffered channel, similar to what is done with the nodeUpdates.

aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd,aakselrod/lnd