Cleaner rover shutdown

[Terracom12]

Currently shutdown is done by killing the tmux server, which in turn quickly kills each of the processes running locally and remotely.

This seems to break some processes that require clean-up behavior like the LiDAR driver. Perhaps try sending SIGINT to all processes first through some tmux facility?

There are certainly nicer ways to solve this with more integration with launch_ros and maybe systemd as an alternative to a tmux server. See the subsequent issue on a more streamlined launch system.