vp9-rtc: Fix to speed 4 for real-time mode

Fix some speed feature settings for speed 4
in real-time mode.

Use rd pickmode (i.e.,nonrd_pick_mode=0), but
use variance partitioning. Allow aq-mode=3 to
work at speed 4 and modify some other speed settings.
This makes it much faster than the current speed 4,
and still better quality than speed 5.

Change-Id: I94ec43ccac022030a75b5a528703be0c37f9a35c
2 files changed