Support multiple daily process locking backends with distributed polling (#11896)

* Implement locks in the file cache

* Replace custom locks

* implement restore lock
Used when re-hydrating

* remove legacy use statements

* Add class descriptions

* Fix style

* Default to database cache driver

* missed cache_locks table
prevent chicken-egg issue

* style fixes

* Remove custom file lock implementation

* missed items from file cache

* Update schema definition
hmm, other schema noise must be from manual modification as this is generated from a freshly migrated db.

* require predis, it is pure python, so no harm in adding

* and set predis as the default client

discovery.php

@@ -8,9 +8,6 @@
  *
  * @copyright  (C) 2006 - 2012 Adam Armstrong
  */
-
-use LibreNMS\Util\FileLock;
-
 $init_modules = ['discovery'];
 require __DIR__ . '/includes/init.php';
 
@@ -33,7 +30,7 @@ if (isset($options['h'])) {
         $where = ' ';
         $doing = 'all';
     } elseif ($options['h'] == 'new') {
-        $new_discovery_lock = FileLock::lockOrDie('new-discovery');
+        $new_discovery_lock = Cache::lock('new-discovery', 300);
         $where = 'AND `last_discovered` IS NULL';
         $doing = 'new';
     } elseif ($options['h']) {
@@ -138,7 +135,7 @@ if ($discovered_devices) {
     }
 }
 
-if ($doing === 'new') {
+if (isset($new_discovery_lock)) {
     $new_discovery_lock->release();
 }