Revert "Add a default serial on handler restart"

This reverts commit f1c68960d5.

defaults/main.yml

@@ -8,7 +8,6 @@ mysql_vendor: 'mariadb'
 mysql_root_password: 'change_me_NOW'
 mysql_notify_restart: true
 mysql_upstream_apt_src: false
-mysql_serial_restart: 1
 
 # -------------------------------------
 # Configuration

handlers/main.yml

@@ -3,4 +3,3 @@
 - name: restart mysql
   action: service name=mysql state=restarted enabled=yes
   when: mysql_notify_restart
-  serial: "{{ mysql_serial_restart }}"