Explicitly disable queueing in functional test.

This was previously relying on the environment not having the ENABLE_QUEUE
variable set, rather than making sure queueing was disabled.
Disable queue behaviour in integration tests.

This doesn't actually break the functionality in the tests, but most of the
HTTP-level tests are checking the response's `#ok?` method, which asserts a
200 response code, rather than the 202 we return when running asynchronously.