[Bug]Duplicate request headers are added

Method copyResponseHeader repeatedly add request headers when servletResponse contains header, so need to add judgement.

protected void copyResponseHeader(HttpServletRequest servletRequest,
                                  HttpServletResponse servletResponse, Header header) {
    String headerName = header.getName();
    if (hopByHopHeaders.containsHeader(headerName))
      return;
    String headerValue = header.getValue();
    if (headerName.equalsIgnoreCase(org.apache.http.cookie.SM.SET_COOKIE) ||
            headerName.equalsIgnoreCase(org.apache.http.cookie.SM.SET_COOKIE2)) {
      copyProxyCookie(servletRequest, servletResponse, headerValue);
    } else if (headerName.equalsIgnoreCase(HttpHeaders.LOCATION)) {
      // LOCATION Header may have to be rewritten.
      servletResponse.addHeader(headerName, rewriteUrlFromResponse(servletRequest, headerValue));
    } else {
      servletResponse.addHeader(headerName, headerValue);
    }
  }

Start at copyResponseHeader(HttpServletRequest, HttpServletResponse, Header) and inspect how servletResponse headers are handled before addHeader. Reproduce the duplicate-header case described in issue 244; done means repeated request headers are not added while the existing cookie and Location handling still works.