message: rpc: further constrain the libevent workaround
  The bug was introduced in 2.1.6-beta, versions before that don't need the
  workaround.
  Github-Pull:
  Rebased-From:
diff: @@ -241,7 +241,7 @@ static std::string RequestMethodString(HTTPRequest::RequestMethod m)
  static void http_request_cb(struct evhttp_request* req, void* arg)
  {
  // Disable reading to work around a libevent bug, fixed in 2.2.0.
  - if (event_get_version_number() < 0x02020001) {
  + if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
  evhttp_connection* conn = evhttp_request_get_connection(req);
  if (conn) {
  bufferevent* bev = evhttp_connection_get_bufferevent(conn);
  @@ -615,7 +615,7 @@ void HTTPRequest::WriteReply(int nStatus, const std::string& strReply)
  evhttp_send_reply(req_copy, nStatus, nullptr, nullptr);
  // Re-enable reading from the socket. This is the second part of the libevent
  // workaround above.
  - if (event_get_version_number() < 0x02020001) {
  + if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
  evhttp_connection* conn = evhttp_request_get_connection(req_copy);
  if (conn) {
  bufferevent* bev = evhttp_connection_get_bufferevent(conn);
  