Always mark device last_discovered (#15218)

Previously, if the device was ping only, it wasn't marked as discovered.
Now we always run discovery, but basically all it does is update last_discovered.

discovery.php

@@ -102,8 +102,20 @@ if (! empty(\LibreNMS\Config::get('distributed_poller_group'))) {
 
 global $device;
 foreach (dbFetch("SELECT * FROM `devices` WHERE disabled = 0 $where ORDER BY device_id DESC", $sqlparams) as $device) {
+    $device_start = microtime(true);
     DeviceCache::setPrimary($device['device_id']);
-    $discovered_devices += (int) discover_device($device, $module_override);
+
+    if (discover_device($device, $module_override)) {
+        $discovered_devices++;
+
+        $device_time = round(microtime(true) - $device_start, 3);
+        DB::table('devices')->where('device_id', $device['device_id'])->update([
+            'last_discovered_timetaken' => $device_time,
+            'last_discovered' => DB::raw('NOW()'),
+        ]);
+
+        echo "Discovered in $device_time seconds\n\n";
+    }
 }
 
 $end = microtime(true);