Fixes/hides a deadlock when running test_sale_order with either a single
database or a db_filter making a single database visible: the test
causes a report to be printed, which invokes wkhtmltopdf, which tries to
fetch assets using the registry which is being loaded. The asset request
thus waits on a lock which is held by the test which waits on the asset,
deadlocking the whole thing.
Using HttpCase means we're using the test_cr or something and bypassing
the deadlock, instead the asset requests just 404 as they do when using
the nodb routing.
Xavier Morel
a43b220b33