Implement getQueryParameter() function on Credentials (to provide an option for those needing parameters within context updates). Do not read parameters within AuthenticatingHttpServlet.

guacamole/src/main/java/net/sourceforge/guacamole/net/basic/AuthenticatingHttpServlet.java

@@ -256,16 +256,10 @@ public abstract class AuthenticatingHttpServlet extends HttpServlet {
                 return;
             }
 
-            // Retrieve username and password from parms
-            String username = request.getParameter("username");
-            String password = request.getParameter("password");
-
             // Build credentials object
             Credentials credentials = new Credentials();
             credentials.setSession(httpSession);
             credentials.setRequest(request);
-            credentials.setUsername(username);
-            credentials.setPassword(password);
 
             // Get authorized context
             try {