[Follow person] The robot doesn't spawn

[OscarMrZ]

When launching the simulator and the robot in the Follow Person exercise, the robot doesn't spawn properly because the robot spawner node executes before gazebo server is properly setup.

To solve this, a simple delay could be added to ensure the spawn always occurs after gazebo is running.

[OscarMrZ]

Also, the simulator should be started paused, so it waits for the start exercise signal to move the person.