Fixes for key frame coding at speed 5.
Keep the same transform cutoff and partition selection for speed 5 as in speeds >=6 (non-rd speed settings). Existing setting for key frame at speed 5 allowed transform size up to 32x32 on key frames, and did not allow for 4x4 block partition size. This created more visual artifacts on first few frames. avgPSNR/overallPSNR/SSIM gains of 0.2/0.7/0.8 for rtc_derf(low-res) set, and 0/0.7/1.1 gains for rtc set. Change-Id: I8c139ec6c9bb74e14b4ffbad5f12e94f18a59c0b