Fix swarming_load_test_bot.py.
Fix swarming_load_test_bot.py.

The (old) bot API changed but the load test wasn't updated accordingly.

There will be a follow up to improve it substantially from there.

R=vadimsh@chromium.org
BUG=

Review URL: https://codereview.appspot.com/121740044

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py