run_unittests returns a proper exit status. It'll now return 0, 1 or 2, corresponding to the number of test invocations (either user or root privileged) that failed. BUG=None TEST=Script runs and returns correct status. Change-Id: I0d5bd8436b1a9972337f34073321239d94565748 Reviewed-on: https://gerrit.chromium.org/gerrit/31006 Reviewed-by: Don Garrett <[email protected]> Commit-Ready: Gilad Arnold <[email protected]> Tested-by: Gilad Arnold <[email protected]>