wait_for_server can return before result or feedback topic is fully connected

[c-andy-martin]

The check for subscription to the result and feedback topics in wait_for_server is insufficient to actually having a completed subscription. The check simply checks if we are tracking a connection in the connection list. Unfortunately, connections are added to the list in rospy before the underlying transport is connected. In certain scenarios, this can take enough time to miss a result from the first submitted goal, causing wait_for_result to timeout. A fix is submitted in #180