List available metadata

    CLI Example:

    .. code-block:: bash

        salt '*' mdata.list

def list_():
    '''
    List available metadata

    CLI Example:

    .. code-block:: bash

        salt '*' mdata.list
    '''
    mdata = _check_mdata_list()
    if mdata:
        cmd = '{0}'.format(mdata)
        return __salt__['cmd.run'](cmd, ignore_retcode=True).splitlines()
    return {}