tests: Disable non-test logging unless level <= DEBUG
tests: Disable non-test logging unless level <= DEBUG

This makes it easier to see the test results, and it hides some
scary-looking but intentional error messages.

This code will likely have to be updated if/when we change the logging
library (see issue #1922).

storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite