Currently, the best quality mode in VP9 is not very well developed,
and unnecessarily makes the encode too slow. Hence the command line
default is changed to "good" quality. Also, the number of passes
default is changed to 2 passes as well, since 1-pass encoding is
not very efficient in VP9.

Besides, a number of VP9 defaults are set to the currently
recommended settings. With these changes, vpxenc
run with --codec=vp9 --kf-max-dist=9999 --cpu-used=0 should
work about the same as our borg results.
Note when the --cpu-used=0 option is dropped there will be a slight
difference in the output, because of a difference in the cpu-used
value for the first pass. Specifically, the default when unspecified
is to use cpu_used=1 for the first pass and cpu_used=0 for the
second pass. But when specified, both passes will use the cpu-used
value specified.

Note that this also changes the default for VP8 as being "good"
but other options stay unchanged.

Change-Id: Ib23c1a05ae2f36ee076c0e34403efbda518c5066