going back to the login error page is confusing (#641)

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@3733 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/Hudson.java

@@ -1274,7 +1274,7 @@ public final class Hudson extends View implements ItemGroup<TopLevelItem>, Node
             rsp.sendRedirect2("noPrincipal");
 
         String from = req.getParameter("from");
-        if(from!=null && from.startsWith("/"))
+        if(from!=null && from.startsWith("/") && !from.equals("/loginError"))
             rsp.sendRedirect2(from);    // I'm bit uncomfortable letting users redircted to other sites, make sure the URL falls into this domain
         else
             rsp.sendRedirect2(".");