Don't make HardwareRenderer calls in the finalizer

 Bug: 13902530
 Don't try to set the RenderNode's displayListData to 0 in the finalizer.
 The HardwareRenderer may have already been finalized and it's not valid
 to make calls into HardwareRenderer from another thread anyway.

 The fix is that now that RenderNode is a refcounted object, this step
 can be skipped entirely. The RenderNode destructor handles deleting
 its DisplayListData if it needs to.

Change-Id: Ieab75575b98c24678a531dd5aa41a2d0afde0eef