Change apinger to dpinger on the fly

when processing the Service Watchdog list.
Leave the permanent update of the list for when the user next edits Service Watchdog settings.
This is an alternate version of #105

sysutils/pfSense-pkg-Service_Watchdog/files/usr/local/pkg/servicewatchdog.inc

@@ -107,6 +107,10 @@ function servicewatchdog_check_services() {
 	$a_pwservices = &$config['installedpackages']['servicewatchdog']['item'];
 
 	foreach ($a_pwservices as $svc) {
+		// apinger became dpinger in pfSense 2.3
+		if ($svc['name'] == 'apinger') {
+			$svc['name'] = 'dpinger';
+		}
 		if (!get_service_status($svc)) {
 			$descr = strlen($svc['description']) > 50 ? substr($svc['description'], 0, 50) . "..." : $svc['description'];
 			$error_message = "Service Watchdog detected service {$svc['name']} stopped. Restarting {$svc['name']} ({$descr})";