As we use now simple action server for exe_path, every new plan will stop the action, set the new plan, and restart exe_path. Following #64, this is not only ugly, but also will introduce a zero-velocity command at every new plan.

Possible solution: use a normal action server so every new goal received while running a previous one just updates the path we are already following, without preempting the previous goal.
🤔 actually, we can abuse a bit this to provide a simple interface for pause / resume: empty path for pause, non-empty to resume.