Ensure that the default fullscreen params have a corner radius

- Until we update the fullscreen params, the tmp params have no radius
  so in cases where a new task is created while overview is open, or if
  we go to overview from home immediately after starting launcher for
  the first time, there would be no corners

Bug: 158050383
Test: Kill launcher, swipe up to overview, ensure tasks have corner
      radius (if device supports it)
Change-Id: I6b72c1a401b9203da3acffc88578c1ed743c8f68