Fix DB timezone validation (#14035)

* Fix DB timezone validation
Restore DB session timezone after schema dump

* happy styleci is good styleci

LibreNMS/DB/Schema.php

@@ -407,6 +407,8 @@ class Schema
             }
         }
 
+        DB::statement('SET TIME_ZONE=@@global.time_zone'); // restore session timezone
+
         return $output;
     }
 }