Move the checking of mWindowAttributesChanged closer to relayoutWindow

It prevents additional relayoutWindow after the first performTraversals
if there is a SurfaceView in the view tree. It happens from
host.dispatchAttachedToWindow to SurfaceView#onAttachedToWindow
and then requestTransparentRegion that changes mWindowAttributesChanged
to true. So it is useless to clear mWindowAttributesChanged before the
path in the case.

Bug: 140407614
Test: The ViewRootImpl#relayoutWindow is only called once when
      launching a simple activity which contains a SurfaceView.

Change-Id: Id49226cab0e9407e6d76e6446f490145b0929594