Signup page redirects already logged in users properly

Change-Id: I29ba614ab924fb8d6e2f5380fe4d384607623ab8

jams-server/src/main/resources/webapp/js/signup.js

@@ -25,6 +25,7 @@ var date = new Date();
 var minutes = 15;
 
 checkAdminAccountStatus();
+checkAuthentication();
 
 $(".form-submit").click(function (event) {
   event.preventDefault();