make sure SF initialization is ran at target priority and correct thread group

SF can spawn threads (indirectly) during initialization
and we want those to be spawned at URGENT_DISPLAY_PRIORITY
(in theory they should set their own, but some code lives
in vendor libraries and doesn't).

Bug: 10430209
Change-Id: I5b3a8f979297de287614c8eafd8267bef1176e4b