fix(cluster): set keepalived vrrp_script weight to -20 for instant failover

src/ClusterManager.php

@@ -342,7 +342,7 @@ class ClusterManager
         $conf[] = "vrrp_script chk_asterisk {";
         $conf[] = "    script \"/etc/keepalived/scripts/check_asterisk.sh\"";
         $conf[] = "    interval 2";
-        $conf[] = "    weight 2";
+        $conf[] = "    weight -20";
         $conf[] = "    fall 2";
         $conf[] = "    rise 2";
         $conf[] = "}";