This is a patch I filed against upstream[1] a while ago. As it isn't
merged yet and fixes configurations with all stats enabled in knot
(otherwise it'd crash when sending a request to `localhost:9433`), I
decided that it makes sense to add it to the package directly.
I extended the test to make sure that it only passes with this patch.
[1] https://github.com/ghedo/knot_exporter/pull/6
75c5a703ab