[autotest] test_that summarizes results via generate_test_report script

This CL gets test_that to use the generate_test_report script (supplied
in the chroot by crostest_utils) to summarize the results of a run. This
is a temporary measure to give some nice result summarizing while
sidestepping the bigger problem of re-using the TKO / run_suite result
summarizing code.

BUG=chromium:243431
TEST=Ran tests in the chroot using test_that. A results summary was
displayed at the end.
Change-Id: Ia5a4f00e9c27a696887eea358df6d27886cf7526
Reviewed-on: https://gerrit.chromium.org/gerrit/60820
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
2 files changed