Logging: Don't log to console for xhr request not sending `cmdMode` to prevent invalid JSON responses

[mjansenDatabay]

This PR fixes an issue with popular community plugins (like UserTakeover) sending xhr requests which do not include a cmdMode=async query parameter.

If the console logging is enabled in the ILIAS logging administration, JSON HTTP responses are not valide anymore because \Monolog\Handler\BrowserConsoleHandler appends a <script> tag to the response body.