test: mark invalid test as xfail

This test looks for some behavior on non-chunked HTTP requests.

It now fails because it looks like recent versions of Docker Engine
ALWAYS return chunked responses (or perhaps this specific response
changed somehow to now trigger chunking whereas it did not previously).

The actual logic it's trying to test is also unusual because it's
trying to hackily propagate errors under the assumption that it'd get
a non-chunked response on failure, which is...not reliable. Arguably,
the chunked reader should be refactored somehow but that's a refactor
we can't really commit to (and it's evidently been ok enough as is
up until now).

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

tests/integration/regression_test.py

@@ -8,6 +8,7 @@
 
 
 class TestRegressions(BaseAPIIntegrationTest):
+    @pytest.mark.xfail(True, reason='Docker API always returns chunked resp')
     def test_443_handle_nonchunked_response_in_stream(self):
         dfile = io.BytesIO()
         with pytest.raises(docker.errors.APIError) as exc: