Added message to guardlog help to direct to guardctrl log for past log viewing

This should help direct those who have forgotten or are still trying to learn the guardian commands.

bin/guardlog

@@ -5,6 +5,8 @@ usage: guardlog [node [node ...]]
 
 Follow guardian logs in special X window.
 If no node is specified all node logs will be followed.
+
+To view past guardian logs, use the "guardctrl log" command.
 EOF
     exit
 fi