Exchange SMTP Graphs.

the leading slash seems to cause the graphs not to display, if it's removed it seems to work properly.

— exchange_trans_smtp.inc.php.old 2015-03-26 11:56:43.782530063 +1100
+++ exchange_trans_smtp.inc.php 2015-03-26 11:45:13.218506741 +1100
@@ -16,7 +16,7 @@
$colours = "mixed";
$nototal = 1;
$unit_text = "Queues";
-$rrd_filename = get_rrd_path($device, "/wmi-app-exchange-smtp.rrd");
+$rrd_filename = get_rrd_path($device, "wmi-app-exchange-smtp.rrd");

if (is_file($rrd_filename))
{