test: fix test-stream2-httpclient-response-end
requested to merge github/fork/MylesBorins/fix-flaky-test-stream2-httpclient-response-end into master
It is possible for test-stream2-httpclient-response-end to be flaky if the http response is read via two syscalls.
This test ensures the output of res.read() is not null or undefined before concatenating.