Fix 2209086: Clean up visual glitches in SlidingTab for lock and incall screen.

This fixes the following glitches:
- flash at the end of animation as the widget resets. Fix: new "hold" animation holds the view for 1 second, allowing it to transition before we reset the view.
- target flashing. Fix: remove AlphaAnimation when we want to hide the target.
- bar appears to get stuck at edge. Fix: sliding bar now slides fully offscreen when hold == true.  Added setHoldAfterTrigger() method to allow InCallScreen and LockScreen to have different behaviors.
- view continues to animate when shown again. Fix: reset the animations and sliders when the view is hidden.

Tested:
	Answer/Decline call on CDMA and GSM device.
	Unlock phone and toggle sound on/off in LockScreen on both devices.