Bug 221208

Similar to https://bugs.webkit.org/show_bug.cgi?id=196248, is_test_mode_enabled variable should default to True in order to avoid accidentally running production settings on a local/test instance. Currently we need to explicitly add an environment variable BUILDBOT_TESTING in order to indicate test instance. If someone forgets to set this environment variable on a local instance, he/she would run with production settings. Currently it's very easy to make this mistake. We should reverse the logic to make it harder to do such mistake. We should instead require to set an environment variable BUILDBOT_PRODUCTION on production server. It will be a one time configuration on the production server (by configuring environment variable in a manner that persist across reboots and various shell sessions).