mxvlan.service: Order after network.service

[donald]

mxvlan.service expects the (renamed) network interfaces to be available. Currently it races with network.service which does the renaming. Fix that.

[pmenzel]

This is supposed to resolve https://github.molgen.mpg.de/mariux64/mariux64-issues/issues/127.

[pmenzel]

From systemd.special(7):

   network.target
       This unit is supposed to indicate when network functionality is available, but it is only
       very weakly defined what that is supposed to mean. However, the following should apply at
       minimum:

       o   At start-up, any configured synthetic network devices (i.e. not physical ones that
           require hardware to show up and be probed, but virtual ones like bridge devices and
           similar which are created programmatically) that do not depend on any underlying
           hardware should be allocated by the time this target is reached. It is not necessary for
           these interfaces to also have completed IP level configuration by the time
           network.target is reached.

       o   At shutdown, a unit that is ordered after network.target will be stopped before the
           network -- to whatever level it might be set up by then -- is shut down. It is hence
           useful when writing service files that require network access on shutdown, which should
           order themselves after this target, but not pull it in. Also see Running Services After
           the Network Is Up[1] for more information.

       It must emphasized that at start-up there's no guarantee that hardware-based devices have
       shown up by the time this target is reached, or even acquired complete IP configuration. For
       that purpose use network-online.target as described above.

[pmenzel]

No idea if VLANs classify as “any configured synthetic network devices”.