Fix behavior when canceling a motion

[adolfo-rt]

This is the current output produced when a motion is canceled (timestamps removed for brevity):

[ WARN] [.]: controller left_arm_controller failed with err 0
[ WARN] [.]: controller head_controller failed with err 0
[ WARN] [.]: controller right_arm_controller failed with err 0
[ WARN] [.]: controller torso_controller failed with err 0
[ INFO] [.]: Motion played successfully.
[ERROR] [.]: You are attempting to call methods on an uninitialized goal handle

Things to look into:

• The last message suggests something fishy in the actionlib logic.
• The Motion played successfully. message is not correct. It should say something more like Motion execution was canceled.. This point might be related to the previous one.
• When a motion is canceled, we should probably discriminate between the cases of the play_motion goal being canceled, and somebody preempting our controller goals. Ideally, a single log statement could reflect that. Examples:

Motion execution was canceled. Motion execution failed. Controller: 'foo' failed with error 0.

[po1]

This is because the final states of the controller goals are not propagated appropriately. The internal API is doing information withholding. Maybe I can talk some sense into it.

[adolfo-rt]

Maybe I can talk some sense into it.

Be kind