fixed rrd path

Author: Sam Banks

templates/agent-conf.d/cacti.yaml.erb

@@ -8,5 +8,5 @@ instances:
   - mysql_host: <%= @mysql_host %>
     mysql_user: <%= @mysql_user %>
     mysql_password: <%= @mysql_password %>
-    rrd_path: <%= @mysql_path %>
+    rrd_path: <%= @rrd_path %>