[autotest] fail test_that if autotest_quickmerge fails

BUG=chromium:310849
TEST=Verified that test_that dies if autoserv fails.

Change-Id: I24e628e5d6c3ce374627183b0dd2e35508f5fe83
Reviewed-on: https://chromium-review.googlesource.com/174451
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
1 file changed