message: [dbus] fixed some dbus issues during destruction
diff: @@ -191,6 +191,7 @@ exit:
  ControllerWpantund::ControllerWpantund(const char *aInterfaceName) :
  mDBus(NULL)
  {
  + mInterfaceDBusName[0] = '\0';
  strncpy(mInterfaceName, aInterfaceName, sizeof(mInterfaceName));
  }
  @@ -244,6 +245,7 @@ exit:
  if (mDBus)
  {
  dbus_connection_unref(mDBus);
  + mDBus = NULL;
  }
  otbrLog(OTBR_LOG_ERR, "NCP failed to initialize!");
  }
  @@ -326,7 +328,7 @@ exit:
  otbrError ControllerWpantund::TmfProxyStop(void)
  {
  - return TmfProxyEnable(FALSE);
  + return mInterfaceDBusName[0] == '\0' ? OTBR_ERROR_NONE : TmfProxyEnable(FALSE);
  }
  void ControllerWpantund::UpdateFdSet(fd_set &aReadFdSet, fd_set &aWriteFdSet, fd_set &aErrorFdSet, int &aMaxFd)
  