test-http-bad-server: align output by using `;`
This is the only message using a `,` instead of `;` and that seems
unintentional. I am unifying the message before unigying the code.
Differential Revision: https://phab.mercurial-scm.org/D12039
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.