Refactor tests that might be unnecessary

[surister]

in test_http.py, for example tests that use: https://github.com/crate/crate-python/blob/371e12576f508d1250b267690237e07779c3c935/tests/client/test_http.py#L563 Do not seem to be very useful, we setup an HTTP server that parses things from the headers and puts the parsed stuff to a dictionary, then we check that that dictionary has what we expected.

Why are we testing this on a threaded HTTP server, we could literally just get the headers from a request and check that it's what we'd expect, without any overhead of setting up a thread and an http server. Other tests that also start an http server have the same issue, we could test the exact same thing without all of this machinery.