Add scriptlet to enable nss-resolve
    
    The default line is
    > hosts: files dns myhostname
    Some people might insert mymachines, most likely as:
    > hosts: mymachines files dns myhostname
    The scriptlet for nss-mdns inserts mdns before dns:
    > hosts: ... files mdns4_minimal [NOTFOUND=return] dns ...
    
    The scriptlet replaces 'files dns myhostname' with
    > resolve [!UNAVAIL=return] myhostname files dns
    This follows the upstream recommendation. myhostname is ordered earlier
    because
    a) it's more trustworthy than files or especially dns
    b) resolve synthetizes the same answers as myhostname, so it doesn't
       make much sense to have myhostname at any other place than directly
       after resolve, so that if resolve is not available, we get answers for
       the names that myhostname is able to synthesize with the same priority.
    
    See https://fedoraproject.org/wiki/Changes/systemd-resolved.