SF: use the new work duration when avoiding a vsync skip

When flags::dont_skip_on_early() is set, the scheduler will avoid
skipping a vsync and instead try to present it even if the work
duration is longer than the time to the next vsync. This CL fixes
a bug where we used the old work duration instead of the new one,
leading to starting the nex frame too late (and missing it).

Bug: 273702768
Bug: 307912181
Test: presubmit (including unit test fixes)
Change-Id: I990af3b56a2f345dd192b17f09673a8710a742fc