authentication error page doesn't have the user name field, and in any case...

authentication error page doesn't have the user name field, and in any case there's no need to set it here, so skip it.

core/src/main/java/hudson/tools/JDKInstaller.java

@@ -370,7 +370,6 @@ public class JDKInstaller extends ToolInstaller {
             try {
                 // JavaScript check page. Just submit and move on
                 HtmlForm loginForm = html.getFormByName("myForm");
-                loginForm.getInputByName("ssousername").setValueAttribute(u);
                 page = loginForm.submit(null);
                 continue;
             } catch (ElementNotFoundException e) {