IMU Test - Fix logic of "no_legs" parameter

[martinaxgloria]

With #72, we added the possibility to parse the remoteControlBoards list within the test_imu.ini file to search for the legs. Unfortunately, I found an error in the logic implementing this functionality since:

  for (auto part : partsList)
  {
      if(part.find("leg") != std::string::npos)
      {
          strParam = "no_legs";
      }
  }

searches if the substring leg is found and, if yes, it passes to the move.sh the parameter no_legs. This is the opposite of expected behavior.

This PR should fix this error

cc @pattacini