[tl_detector] tl detection is never run when playing rosbag

[ivovandongen]

When using the Rosbag provided, the pose is never set in the tl_detector node and as such the nearest traffic light cannot be found, thus detection never runs.

We need to investigate if this is a problem on our end or not and if we can work around it.

• Callback (doesn't get called): https://github.com/ivovandongen/CarND-Capstone/blob/master/ros/src/tl_detector/tl_detector.py#L70
• Necessity for pose information in tl detection: https://github.com/ivovandongen/CarND-Capstone/blob/master/ros/src/tl_detector/tl_detector.py#L165