[autotest] Use a server test as the sanity build test

The sanity suite takes 15 mins, which is too long.
Use a server test that does nothing as the sanity test.
It saves us some time spent on installing/uninstalling autotest
packages.

CL-DEPEND=CL:238088
TEST=Run the sanity suite.
BUG=chromium:432655

Change-Id: I00e5102c9796573a6c0bdd5da021e1c1e531bebd
Reviewed-on: https://chromium-review.googlesource.com/238094
Reviewed-by: Dan Shi <dshi@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
Trybot-Ready: Fang Deng <fdeng@chromium.org>
2 files changed