vp9-rc: Fix key frame setting in external RC
vp9-rc: Fix key frame setting in external RC

Bug: b/257368998

Change-Id: I03e35915ac99b50cb6bdf7bce8b8f9ec5aef75b7

webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx