lnd_test: alter testUnconfirmedChannelFunding to work with Neutrino
lnd_test: alter testUnconfirmedChannelFunding to work with Neutrino

We slightly alter testUnconfirmedChannelFunding to instead of using an
external deposit to test unconfirmed channel funding, we use one of our
own unconfirmed change outputs.

This is done since Neutrino currently has now way of knowing about
incoming unconfirmed outputs.

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