fixed minor issues

roles/mysql/tasks/mysql_client.yml

 ---
 - name: "Installing MySQL Debian"
   apt: name="{{ item }}" update_cache=yes cache_valid_time=3600 state=present
-  with_items: client_packages
+  with_items: "{{ client_packages }}"
   sudo: true
   when: ansible_os_family == "Debian"
 
 - name: Installing MySQL RedHat
   yum: name="{{ item }}" state=present
-  with_items: client_packages
+  with_items: "{{ client_packages }}"
   sudo: true
   when: ansible_os_family == "RedHat"

roles/mysql/tasks/mysql_server.yml

 ---
 - name: "Installing MySQL Debian"
   apt: name="{{ item }}" update_cache=yes cache_valid_time=3600 state=present
-  with_items: server_packages
+  with_items: "{{ server_packages }}"
   sudo: true
   when: ansible_os_family == "Debian"
 
 - name: Installing MySQL RedHat
   yum: name={{ item }}
-  with_items: server_packages
+  with_items: "{{ server_packages }}"
   sudo: true
   when: ansible_os_family == "RedHat"