add system property to set auto refresh interval

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@32336 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/Functions.java

@@ -444,7 +444,7 @@ public class Functions {
             response.addCookie(c);
         }
         if (refresh) {
-            response.addHeader("Refresh", "10");
+            response.addHeader("Refresh", System.getProperty("hudson.Functions.autoRefreshSeconds", "10"));
         }
     }