Bug 44651 - Add support for round-trip testing of non-English wiki pages

Our current round-trip server (in js/tests/server) only supports titles from a
single wiki, which is statically configured in the test runner config
(js/tests/client).

In preparation for deployments to non-English wikis, we need to do some
round-trip testing with content from those wikis.

Added a comment near the hacky workaround that we use to kill clients.

Co-authored-by: C. Scott Ananian <cscott@cscott.net>
Co-authored-by: Mark Holmquist <mtraceur@member.fsf.org>

Change-Id: Idc433e435a6de42b9dc269d0f6850c68e0e361d2