When you say "stop", do you want it to hold the pose at the point where you stopped it? Or do you want it to return to some idle pose/animation?
You could just call ClearTrack(0). ClearTracks is fine. Though it may not work as you expect in 3.5 depending on the AnimationState settings.
If you want it to keep applying, you could also set the TrackEntry.TimeScale to 0.
skeletonAnimation.state.GetCurrent(0).TimeScale = 0;
This stops the animation from progressing but still applies it normally.
If you want it to return to some idle pose, just set the animation to a definite idle animation using SetAnimation
