Cut at specified angle leads to deadlock

[sts-thm]

The cut_angle parameter and functionality introduced by #138 leads to a deadlock inside a while(true)-loop, for specific values of the cut_angle parameter in relation to the FOV specified in the velodyne's user interface.
I found out about this issue using a VLP16 and commit ef2345e of this repository.
There are several possible configurations for the relation between the two angles (Start, Stop) specifying the FOV of the velodyne in the velodyne's user interface and the cut_angle parameter (c):

1. 0° < Start < c < Stop < 360°
2. 0° < c < Start < Stop < 360°
3. 0° < Start < Stop < c < 360° <- bad case
4. 0° < Stop < c < Start < 360°
5. 0° < c < Stop < Start < 360°
6. 0° < Stop < Start < c < 360°

For the 3rd configuration the break in the while(true) (https://github.com/ros-drivers/velodyne/blob/master/velodyne_driver/src/driver/driver.cc#L189) is never reached and the loop will never stop.
My solution to this was to replace the lines 180-186 in https://github.com/ros-drivers/velodyne/blob/master/velodyne_driver/src/driver/driver.cc with:

      //if first packet in scan, there is no "valid" last_azimuth
      if (last_azimuth == -1) {
  	 last_azimuth = azimuth;
      	 continue;
      }
      if((last_azimuth < config_.cut_angle && config_.cut_angle <= azimuth)
      	 || ( config_.cut_angle <= azimuth && azimuth < last_azimuth)
      	 || (azimuth < last_azimuth && last_azimuth < config_.cut_angle))

I tested this with the same configurations and it worked.
If you want me to, I can submit a pull request for my fix.

[JWhitleyWork]

Sorry I didn't get to this sooner. I never saw the notification. Please do submit a PR and I will get it tested/reviewed.