SF: set active config state machine

1) Set the desired active config bit
2) On the next vsync, ask HWC to update config.
3) Send a refresh to HWC
4) When the fence comes back, update SF to the new config/refresh rate
   and trigger HWC vsync.

see go/surface-flinger-scheduler for more info

Test: Systrace.
Change-Id: I4ed649668cc6cc23cd3f428b3c92ab1c199c8aa4