utxonursery: update inner loop to use new ChainNotifier API

Within the inner loop of the utxoNursery when waiting for a new
sweepable transaction to be confirmed, we now use the new ChainNotifier
API for ConfirmationEvent’s which exposes additional details as to
exactly where in the chain the transaction was ultimately confirmed.

utxonursery.go

@@ -137,17 +137,18 @@ out:
 				// the output back to the incubator once the
 				// source txn has been confirmed.
 				go func() {
-					confHeight, ok := <-confChan.Confirmed
+					confDetails, ok := <-confChan.Confirmed
 					if !ok {
 						utxnLog.Errorf("notification chan "+
 							"closed, can't advance output %v", outpoint)
 						return
 					}
 
+					confHeight := uint32(confDetails.BlockHeight)
 					utxnLog.Infof("Outpoint %v confirmed in "+
 						"block %v moving to mid-stage",
 						outpoint, confHeight)
-					immatureUtxo.confHeight = uint32(confHeight)
+					immatureUtxo.confHeight = confHeight
 					midStageOutputs <- immatureUtxo
 				}()
 			}