Bad behaviour in PID controller when yaw > 2pi

[krichardsson]

The controller behaves weirdly, possibly ending up in a crash.

How to reproduce:
Write a python script using the high level commander, similar to

    commander = cf.high_level_commander
    commander.takeoff(1.0, 2.0)
    time.sleep(3.0)

    commander.go_to(0, 0, 1, 0, 1)
    time.sleep(1)

    commander.go_to(0, 0, 1, math.pi, 1)
    time.sleep(1)

    commander.go_to(0, 0, 1, math.pi * 2, 1)
    time.sleep(1)

    commander.go_to(0, 0, 1, math.pi * 3, 1)
    time.sleep(1)

    commander.go_to(0, 0, 1, math.pi * 4, 1)
    time.sleep(1)

When reaching yaw > 2 * pi, the crazyflie should do weird things