[autotest] Unhandled run_suite failure treated as infra failure

Any unhandled run_suite exception is not a test failure, and thus
should be considered as a infra failure.

TEST=run_suite -m, confirm normal suite still get the same return code.
stop apache, confirm RPC Timeout will be treated as infra failure.
BUG=chromium:415204

Change-Id: I941ea24b3e603c7b1e939ef389f6f7b2c2181a08
Reviewed-on: https://chromium-review.googlesource.com/218975
Reviewed-by: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
1 file changed