Raise MinQP to allow easier steady-state convergence. Update SVC rate allocator to not waste bandwidth if there's not enough for the highest layer. Bug: webrtc:10257 Change-Id: Iba937bf3c224ffed256308bdb6434be8b5223f84 Reviewed-on: https://webrtc-review.googlesource.com/c/122843 Reviewed-by: Sergey Silkin <ssilkin@webrtc.org> Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org> Cr-Commit-Position: refs/heads/master@{#26710}