Support running notify with variable list

    vars:
        handlers_list:
          - foo
          - bar
    tasks:
        - name: template configuration file
          template: src=template.j2 dest=/etc/foo.conf
          notify: '{{handlers_list}}'

Expected:
TASK: [template configuration file]
*******************************************
changed: [deb7.inter.nos]

NOTIFIED: [foo]
***************************************************************
changed: [deb7.inter.nos]

NOTIFIED: [bar]
***************************************************************
changed: [deb7.inter.nos]

Without this:
TASK: [template configuration file]
*******************************************
changed: [deb7.inter.nos]
ERROR: change handler (['foo', 'bar']) is not defined