fix mysql restart not happening because of missing os specific variable

roles/ansible-mysql-hardening/handlers/main.yml

@@ -1,4 +1,4 @@
 ---
 
 - name: restart mysql
-  service: name='{{}}' state=restarted
+  service: name='{{ mysql_daemon }}' state=restarted

roles/ansible-mysql-hardening/vars/Debian.yml

@@ -1 +1,2 @@
+mysql_daemon: mysql
 mysql_hardening_mysql_conf: '/etc/mysql/my.cnf'

roles/ansible-mysql-hardening/vars/Oracle Linux.yml

@@ -1 +1,2 @@
+mysql_daemon: mysqld
 mysql_hardening_mysql_conf: '/etc/my.cnf'

roles/ansible-mysql-hardening/vars/RedHat.yml

@@ -1 +1,2 @@
+mysql_daemon: mysql
 mysql_hardening_mysql_conf: '/etc/my.cnf'