azimuth_diff if statement for vls128 in raw_data.cc seems wrong

[keenan-burnett]

• OS and Version: Ubuntu 16.04
• ROS Version: Kinetic
• Built from Source or Downloaded from Official Repository: built from source
• Version: commit hash: 29abd0e1361cb7f5eda451d2b51c35eeca45e0d5

Description This if statement doesn't seem correct: https://github.com/ros-drivers/velodyne/blob/29abd0e1361cb7f5eda451d2b51c35eeca45e0d5/velodyne_pointcloud/src/lib/rawdata.cc#L577

For the last block, we don't want to set the azimuth_diff to zero.

Perhaps the statement needs to be changed to:

azimuth_diff = (block == BLOCKS_PER_PACKET - (4*dual_return)-1) ? last_azimuth_diff : 0;