SurfaceFlinger: fix refresh rate override when changing refresh rate

If an app's frame rate is same as the display refresh rate, keep it
on the frame rate override list. The reason for this is if an app
is added to the list after the display refresh rate changed, the few
first frames would be running the the display refresh rate and not at
the override one.

Test: atest FrameRateOverrideHostTest
Test: run TouchLatency while changing refresh rates and collect systrace
Bug: 182544360
Change-Id: I66472a1230affae9336520083f0950ae252ede02