SurfaceFlinger: set refresh rate type when after an attempt to switch

When a refresh rate change is starting we change the offsets to the
new refresh rate to have a better alignment between buffers and the actual
vsync. This change guarantees that we set the correct offset by updating
PhaseOffset after desired config changed.

Test: Let device go to 60Hz due to idle; Open an app; Get systrace; repeat
Bug: 133241520
Change-Id: Id25f5e7d3d280813a106fd311906767d79e4e6ee