fix: inconsistent device discovery (#6518)

There were two or more separate $device arrays during discovery. When one was updated, others were not.
Combine those all.
Make sure the new os is loaded if the os changed.

discovery.php

@@ -121,6 +121,7 @@ if (!empty($config['distributed_poller_group'])) {
     $where .= ' AND poller_group IN('.$config['distributed_poller_group'].')';
 }
 
+global $device;
 foreach (dbFetch("SELECT * FROM `devices` WHERE status = 1 AND disabled = 0 $where ORDER BY device_id DESC", $sqlparams) as $device) {
     discover_device($device, $options);
 }