Add module:default to swarming's app.yaml.
Add module:default to swarming's app.yaml.

Otherwise the performance settings are not used.

R=vadimsh@chromium.org
BUG=

Review URL: https://codereview.appspot.com/157260044

pombreda/swarming,madecoste/swarming,madecoste/swarming,pombreda/swarming,madecoste/swarming,madecoste/swarming,luci/luci-py,pombreda/swarming,luci/luci-py,luci/luci-py,luci/luci-py,pombreda/swarming