Multiple scans are displayed when the FOV is reduced for the Velodyne VLP-16 lidar

[rrr6399]

• OS and Version: Ubuntu 18.04
• ROS Version: Melodic
• Built from Source or Downloaded from Official Repository: lastest master branch off github
• Version: 45636c9

Describe the bug
If the FOV of the VLP-16 is reduced, the Point3D Cloud message contains multiple scans of the data.

To Reproduce
Steps to reproduce the behavior:

1. Use the Velodyne web interface to reduce the FOV
2. Start the Velodyne ROS service connecting to a live VLP-16 lidar
3. Display the lidar data in rviz
4. Notice that multiple scans are being shown at a given time

Expected behavior
One scan per message and data for one scan is shown in rviz.

Here is rviz displaying the lidar data for the reduced FOV

Here is LidarView displaying the lidar data through a direct connection to the lidar

Also, see discussion here:
https://answers.ros.org/question/392144/how-to-receive-and-display-only-one-full-scan-when-the-fov-is-reduced-for-the-velodyne-lidar/