lnwallet: modify CommitSpendNoDelay to directly craft witness
lnwallet: modify CommitSpendNoDelay to directly craft witness

This commit modifies the CommitSpendNoDelay script witness generation
function. We must modify this function as all non-delayed outputs now
also require a key derivation. The current default
signer.ComputeInputScript implementation is unable to directly look up
the public key required as it attempt to target the pub key using the
pkScript.

ddustin/lnd,ddustin/lnd,AndrewSamokhvalov/lnd,aakselrod/lnd,AndrewSamokhvalov/lnd,aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd