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
local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed