play_motion occasionally not getting notified of controller result #39

@v-lopez has observed in a few occassions that even when the joint trajectory controller goals finishes, play_motion is not notified, and its internal busy state is maintained indefinitely. There is no deterministic way to reproduce, but it is likely that this happened when canceling an active goal, and immediately sending a new one.

A stress test could be setup to repeatedly exercise the above sequence, and see if we can reproduce. We should verify if the problem comes from play_motion itself, or whether the joint_trajectory_controller server is somehow not publishing to the result topic.