fix(firewall): log warning if ipv6 nat filter not supported instead of returning an error

- Allow to port forward redirect for IPv4 and not IPv6 if IPv6 NAT is not supported
- Fix #2503

internal/firewall/mocks_test.go

@@ -107,3 +107,15 @@ func (mr *MockLoggerMockRecorder) Info(arg0 interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Info", reflect.TypeOf((*MockLogger)(nil).Info), arg0)
 }
+
+// Warn mocks base method.
+func (m *MockLogger) Warn(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Warn", arg0)
+}
+
+// Warn indicates an expected call of Warn.
+func (mr *MockLoggerMockRecorder) Warn(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Warn", reflect.TypeOf((*MockLogger)(nil).Warn), arg0)
+}