[ros] Fix 'actions' unittest

Closes #228
[ros] waypoint overlay: use standard ROS MoveBaseAction

Since no standard MoveBase service exists, remove it.
[unittest][ros] {data_stream -> topics}

While here, remove useless ROS imports.
[ros] Implement action cancellation and preemption

Updated accordingly ros/actions.py unit-tests.

Closes #119
[unittest][ros] Removed 'services.py' from list of tests

...because no component use ROS services anymore...!
[ros] minor: remove useless imports