surfaceflinger: initialize ActiveConfigInfo fields.

Previously, the two ActiveConfigInfo fields in SurfaceFlinger are
uninitialized upon construction, and when run with debugging code that
slows down open, we reliably hit a case where setRefreshRateType is
called on an uninitialized RefreshRateType, leading to explosion.

Test: booted with libfdtrack
Change-Id: I14520775f8660fee6545d8a354a04ed3674a1597