tests: Instrument tests run in simulation to run quickly

tests: Instrument tests run in simulation to run quickly

We tweak the tests marked as runnable in simulation to run more quickly,
more often then not at the expense of stress testing (which is of an
arguable interest for the initial bring up in simulation). Hopefully the
values chosen still test something, which is not always straightforward.

It does run quickly, the number on an IVB machines are:

$ time sudo IGT_SIMULATION=0 ./piglit-run.py tests/igt.tests foo
[...]
real	2m0.141s
user	0m16.365s
sys	1m33.382s

Vs.

$ time sudo IGT_SIMULATION=1 ./piglit-run.py tests/igt.tests foo
[...]
real	0m0.448s
user	0m0.226s
sys	0m0.183s

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>