openshift-java-client: remove IUser#getAuthKey and IUser#getAuthIV

In UserResource/IUser there are still #getAuthIV #getAuthKey methods that we inherited from the legacy client. They're currently not implement and return <code>null</code>. In the new client the auth keys are passed over to the http client via connection builder. They're not handled by the user any more.

final IHttpClient httpClient = new UrlConnectionHttpClientBuilder().setCredentials(login, password, authKey, authIV)
					.client();

We should simply get rid of them.