Remove nfs requirement for distributed poller (with rrdtool 1.5+)

Use data_update instead of rrd_update/rrd_create and influx_update
Centralize rrd file check so we can check against a remote rrdcached server too
Use rrd_name() to generate rrd file names

html/includes/graphs/application/memcached.inc.php

@@ -1,5 +1,5 @@
 <?php
-$rrd = $config['rrd_dir'].'/'.$device['hostname'].'/app-memcached-'.$app['app_id'].'.rrd';
+$rrd = rrd_name($device['hostname'], array('app', 'memcached', $app['app_id']));
 if (is_file($rrd)) {
     $rrd_filename = $rrd;
 }