Return the disabled services

    CLI Example:

    .. code-block:: bash

        salt '*' service.get_disabled

def get_disabled():
    '''
    Return the disabled services

    CLI Example:

    .. code-block:: bash

        salt '*' service.get_disabled
    '''
    ret = set()
    for name in _iter_service_names():
        if _service_is_upstart(name):
            if _upstart_is_disabled(name):
                ret.add(name)
        else:
            if _service_is_sysv(name):
                if _sysv_is_disabled(name):
                    ret.add(name)
    return sorted(ret)