Set key frame request in VP9 enc wrapper on init.
Set key frame request in VP9 enc wrapper on init.

Since libvpx VP9 enc always issues key frame after reinit.

Bug: none
Change-Id: I3349a38652af9085c35f8ac9d5b9d3e5549daab9
Reviewed-on: https://webrtc-review.googlesource.com/102660
Reviewed-by: Erik Språng <3ab8c90c99d6dd7822e0fad803ab0211dd287ae5@webrtc.org>
Commit-Queue: Sergey Silkin <fc631354f276613a5410ea259cf4618b2846d39b@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#24912}
ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc