code: public void setRemoveUserDefinedAuthHeaders(boolean removeHeaders) {
          client.getParams().setBooleanParameter(HttpMethodDirector.PARAM_REMOVE_USER_DEFINED_AUTH_HEADERS, removeHeaders);
          clientViaProxy.getParams().setBooleanParameter(HttpMethodDirector.PARAM_REMOVE_USER_DEFINED_AUTH_HEADERS, removeHeaders);
      }
docs: Sets whether or not the authentication headers ("Authorization" and "Proxy-Authorization") already present in the request
  should be removed if received an authentication challenge (status codes 401 and 407).
  <p>
  If {@code true} new authentication headers will be generated and the old ones removed otherwise the authentication
  headers already present in the request will be used to authenticate.
  <p>
  Default is {@code false}, i.e. use the headers already present in the request header.
  <p>
  Processes that reuse messages previously sent should consider setting this to {@code true}, otherwise new authentication
  challenges might fail.
  
  @param removeHeaders {@code true} if the the authentication headers already present should be removed when challenged,
  {@code false} otherwise