Support HTTP responses with no body Successful upsertLocalAuthInfo cloud requests returns no body and no content type. BUG=25766813 Change-Id: Id4deb57c8dfea04196f77c80b6f40ce62db9fa6f Reviewed-on: https://weave-review.googlesource.com/1799 Reviewed-by: Alex Vakulenko <avakulenko@google.com>