[DRE-maint] Bug#834686: ruby-httpclient: FTBFS randomly (failing tests)

[Santiago Vila]

Hi.

As a summary, these are the tests which I've seen to fail in my
autobuilders:

(This does not include the failed build logs at reproducible builds).

 267 Error: test_put(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_post_with_header(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_post_with_array_header(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_post(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_post_non_json_body(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_get_not_affected(TestJSONClient): Errno::EADDRINUSE: Address already in use - listen(2)
 267 Error: test_allow_tlsv1(TestSSL): Errno::EADDRINUSE: Address already in use - listen(2)
   3 Error: test_get_content(TestHTTPClient): HTTPClient::ReceiveTimeoutError: execution expired
   1 Error: test_get_content(TestHTTPClient): HTTPClient::SendTimeoutError: execution expired
   1 Error: test_get_async_with_base_url(TestHTTPClient): HTTPClient::ReceiveTimeoutError: execution expired

The number at the left is the number of times the test failed for me.

Either the program is wrong, or the first seven tests are definitely flaky.
I'm unsure about the last three.

Thanks.