Increase test runner thread count for target.

Experiment.

There was no point in increasing the thread count before since
the buildbots were fully bottlenecked by host java compilation.
This has been eliminated by moving the compilation to soong.

Try to slightly increase the thread count to see if we get any
boildbot speedup or if we start having timeout/flake issues.

Test: art/test.py --target -r --optimizing
Change-Id: Iaa705f39e57f09131a6ed65e23d1ca995d3e4fd4
1 file changed