race condition in SimpleActionClient.send_goal

[krixkrix]

Symptoms are that the log contains this:
Got a transition callback on a goal handle that we're not tracking

I started seeing this after the latest noetic actionlib update, which introduced this check:

    def _handle_transition(self, gh):
        if gh != self.gh:
            rospy.logerr("Got a transition callback on a goal handle that we're not tracking")
            return

The problem seems to be that the self.gh is (sometimes) not yet set even the though the goal has been sent.
The error message is logged between the sending of the goal and the return of this statement:

    self.gh = self.action_client.send_goal(goal, self._handle_transition, self._handle_feedback)