consequences of fixing invalid setpoints issue with PX4

[simojo]

after fixing #15, I have run into further issues in which the simulation now terminates itself too quickly after aborting an action that would lead to the said invalid setpoints issue. I need to add some kind of callback that pauses until gazebo finished loading.

[simojo]

Adding ee43b2e removed the immediate issue, but I noticed that the px4 process becomes a zombie process even after killing the clover_train train.py process via rosrun. Odd, but not necessarily obstructive to a finished product.