1.6 - 1.7beta1: Roll is moving during panning

[zasadek]

To invoke and issue: 1. Power on skyline and do some random movements. 2. Put gimbal on leveled floor and remember the roll cage position. 3. Rotate manually gimbal - after 90 degree you will see roll movement. Next 90 degree and the movement will have oposite direction.

Roll movement is about 10-20 degrees. NOTICE that this issue doesn't exist in 1.2.2 firmware.