Refine zoom in and zoom out transition of iamge wallpaper.

We do zoom in from lockscreen to aod1 and zoom out in reverse
transition.

Bug: 124822340
Bug: 133785684
Test: manually set image wallpaper.
Test: Press power key back and forth and observe.
Change-Id: I842f929c730d1234717faa77e32f733f131c6ca0