Refactor TimerAction to allow RosTimer to extend (#512)
Refactor TimerAction to allow RosTimer to extend (#512)

* Refactor to allow RosTimer to extend TimerAction

Signed-off-by: Rebecca Butler <0ab09b420c3f4f686e1f6503c93d3111d2038689@openrobotics.org>

* Add _ prefix to variable names

Signed-off-by: Rebecca Butler <0ab09b420c3f4f686e1f6503c93d3111d2038689@openrobotics.org>
ros2/launch,ros2/launch,ros2/launch