Use window.console instead of just console in vaadinPush to appease IE (#11980)

Change-Id: I6f363e9afc550d70eb451005dcfdfb53e5533273

WebContent/VAADIN/vaadinPush.js.tpl

@@ -3,6 +3,6 @@ window.jQueryVaadin = window.jQuery.noConflict(true);
 (function(jQuery, undefined) {
 	@jquery.atmosphere.js@
 })(jQueryVaadin);
-if (console) {
-	console.log("Vaadin push loaded");
-}
+if (window.console) {
+	window.console.log("Vaadin push loaded");
+}