multi: Add tests to psbt and normal open channel flow.

Itests were added to the normal channel funding flow and the psbt
funding flow using unstable (unconfirmed sweeper inputs).

lntest/rpc/wallet_kit.go

@@ -68,6 +68,16 @@ func (h *HarnessRPC) FundPsbt(
 	return resp
 }
 
+// FundPsbtAssertErr makes a RPC call to the node's FundPsbt and asserts an
+// error is returned.
+func (h *HarnessRPC) FundPsbtAssertErr(req *walletrpc.FundPsbtRequest) {
+	ctxt, cancel := context.WithTimeout(h.runCtx, DefaultTimeout)
+	defer cancel()
+
+	_, err := h.WalletKit.FundPsbt(ctxt, req)
+	require.Error(h, err, "expected error returned")
+}
+
 // FinalizePsbt makes a RPC call to node's FinalizePsbt and asserts.
 func (h *HarnessRPC) FinalizePsbt(
 	req *walletrpc.FinalizePsbtRequest) *walletrpc.FinalizePsbtResponse {