On Windows, Mac, OpenSolaris (verified) and probably Docker (did not verify, but likely),
DNS resolution of "localhost" yields [127.0.0.1, ::1], while on Linux only [127.0.0.1].
HttpClient will try the first address, and in case of failure will try the second address.
For those tests that want to explicitly fail the connection attempt, we don't want them to
try the second address, which likely yields test failures because of unexpected results
(for example, a different exception type).
Signed-off-by: Simone Bordet <simone.bordet@gmail.com>