[autotest] add max_runtime_mins option to test_that.

BUG=b:27174274
TEST=ran tests in Talyn lab.

Change-Id: I8eef3e53f339f1346e249f104933fb63740caa32
Reviewed-on: https://chromium-review.googlesource.com/326928
Commit-Ready: Laurence Goodby <lgoodby@chromium.org>
Tested-by: Laurence Goodby <lgoodby@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
2 files changed