lntest: add method P2PAddr to backend

It is useful if we want to keep bitcoind main itest mode, but connect one node
using neutrino.

lntest/bitcoind_common.go

@@ -85,6 +85,11 @@ func (b BitcoindBackendConfig) Name() string {
 	return "bitcoind"
 }
 
+// P2PAddr return bitcoin p2p ip:port.
+func (b BitcoindBackendConfig) P2PAddr() (string, error) {
+	return fmt.Sprintf("127.0.0.1:%d", b.p2pPort), nil
+}
+
 // newBackend starts a bitcoind node with the given extra parameters and returns
 // a BitcoindBackendConfig for that node.
 func newBackend(miner string, netParams *chaincfg.Params, extraArgs []string,

lntest/btcd.go

@@ -74,6 +74,11 @@ func (b BtcdBackendConfig) Name() string {
 	return "btcd"
 }
 
+// P2PAddr return bitcoin p2p ip:port.
+func (b BtcdBackendConfig) P2PAddr() (string, error) {
+	return b.harness.P2PAddress(), nil
+}
+
 // NewBackend starts a new rpctest.Harness and returns a BtcdBackendConfig for
 // that node. miner should be set to the P2P address of the miner to connect
 // to.

lntest/neutrino.go

@@ -54,6 +54,11 @@ func (b NeutrinoBackendConfig) Name() string {
 	return NeutrinoBackendName
 }
 
+// P2PAddr return bitcoin p2p ip:port.
+func (b NeutrinoBackendConfig) P2PAddr() (string, error) {
+	return b.minerAddr, nil
+}
+
 // NewBackend starts and returns a NeutrinoBackendConfig for the node.
 func NewBackend(miner string, _ *chaincfg.Params) (
 	*NeutrinoBackendConfig, func() error, error) {

lntest/node/config.go

@@ -114,6 +114,9 @@ type BackendConfig interface {
 	// Credentials returns the rpc username, password and host for the
 	// backend.
 	Credentials() (string, string, string, error)
+
+	// P2PAddr return bitcoin p2p ip:port.
+	P2PAddr() (string, error)
 }
 
 // BaseNodeConfig is the base node configuration.