[JTC] improve wraparound tests

[christophfroehlich]

position_error_not_angle_wraparound and position_error_angle_wraparound should check the controller output (and error variable) only with constant position reference but changing position state.

• no interference with trajectory wraparound from [JTC] Angle wraparound for first segment of trajectory #796
• maybe the usage of the state_msg can be removed