Return list of fiber channel HBA WWNs

def fibre_channel_wwns():
    '''
    Return list of fiber channel HBA WWNs
    '''
    grains = {'fc_wwn': False}
    if salt.utils.platform.is_linux():
        grains['fc_wwn'] = _linux_wwns()
    elif salt.utils.platform.is_windows():
        grains['fc_wwn'] = _windows_wwns()
    return grains