rpc: validate closing channel address in open channel requests

Our OpenChannelRPC was accepting invalid values for the closing address
field. If we were able to decode the address we would use it in the
script even if the address is for another bitcoin net.

chanacceptor/rpcacceptor_test.go

@@ -20,7 +20,7 @@ func TestValidateAcceptorResponse(t *testing.T) {
 		customError = errors.New("custom error")
 		validAddr   = "bcrt1qwrmq9uca0t3dy9t9wtuq5tm4405r7tfzyqn9pp"
 		addr, _     = chancloser.ParseUpfrontShutdownAddress(
-			validAddr, &chaincfg.TestNet3Params,
+			validAddr, &chaincfg.RegressionNetParams,
 		)
 	)
 
@@ -124,7 +124,7 @@ func TestValidateAcceptorResponse(t *testing.T) {
 			// Create an acceptor, everything can be nil because
 			// we just need the params.
 			acceptor := NewRPCAcceptor(
-				nil, nil, 0, &chaincfg.TestNet3Params, nil,
+				nil, nil, 0, &chaincfg.RegressionNetParams, nil,
 			)
 
 			accept, acceptErr, shutdown, err := acceptor.validateAcceptorResponse(