Skip updating system bar attributes while relaunching related apps

The appearance of system bars might change while relaunching apps. We
don't report the intermediate state to system UI. Otherwise, it might
trigger redundant effects.

Fix: 255353969
Test: Rotate an app which will relaunch itself during rotation
      (ex: calculator) and see if onSystemBarAttributesChanged
      is only called once.
Change-Id: Ie7241a9bbba19688755bdbb1ddc2abe5f7cb5eac