base1: Make "streaming" test-http test more strict
base1: Make "streaming" test-http test more strict

This test would previously pass if .stream() would not ever be called,
as it would just compare `got == expected == ""`. We know that
test-server sends out exactly the numbers 0 to 9, so make the expected
string static.

We cannot guarantee that we'll get a .stream() call for each individual
written chunk. But let's make sure that we get at least two, to prove
that this is actually happening asynchronously, instead of blocking for
the response to complete.

Rename `at` to `num_chunks` for clarity.

cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit