Return a list off MAC addresses from the named vm

    CLI Example:

    .. code-block:: bash

        salt '*' virt.get_macs <vm name>

def get_macs(vm_):
    '''
    Return a list off MAC addresses from the named vm

    CLI Example:

    .. code-block:: bash

        salt '*' virt.get_macs <vm name>
    '''
    macs = []
    nics = get_nics(vm_)
    if nics is None:
        return None
    for nic in nics:
        macs.append(nic)

    return macs