Fix bug #4796027 left/right padding regression after recent View change (part 2)

- revert previous fix (transforming >=0 to >0)
- initialize mUserPaddingStart and mUserPaddingEnd to -1 in the specific View(Context context) constructor
- cache mUserPaddingStart and mUserPaddingEnd a bit earlier in View(Context context, AttributeSet attrs, int defStyle) constructor
- cache also mUserPaddingStart and mUserPaddingEnd in setPaddingRelative()

Change-Id: Ibe398da7af35f77655d7006444fa49c9c5387f62