basic.target: Pull network

Currently, the network is started more or less by chance, because a few
services have dependencies on network.target, which in fact is even
wrong.

Following the systemd.special(7) and bootup(7) logic, network.target
should be a passive unit and no units should have a Wants or Requires
dependencies on it.

A unit which really wants or requires network connectivity should depend
on network-online.target, on the other hand, typicall service units
really don't need network connectivity.

However, Mariux64 is kind of special in some ways:

- We have services started on dedicated IP addresses and vlan
  interfaces. For the bind to work, the vlan interfaces have to exist
  and also the ip addreses must be configured, unless the service uses
  the IP_FREEBIND socket option or we globally enable ip_nonlocal_bind.

- We have a global filesystem namespace using automounted remote
  filesystems. Services, cron-jobs and user sessions might all require
  the network to be available to access the files which happen to be on
  a remote systems.

So in fact we shouldn't start normal user processses via mxstartup or
cron or login sessions before we tried our best to provide network
connectivity.

So for Mariux64, which havenly depends on the network, make the attempt
to start the network part of the basic os service, available with
basic-target.

After this change, all normal services can assume, that the ip
interfaces are available, the ip addresses have been configured (if not
done by mxstartup), we've waited a reasonable time for the link to come
up, the default route has been set, automount-paths are available, name
resolution works and important services like the default nameserver or
mxshadow are available. At least in the realm of the local systems
responsibility, of course, things will still fail if the network or the
peer server have issues.

install.sh

@@ -265,6 +265,8 @@ install_data misc_etc_files/request-key.d/id_resolver.conf \
                                                           "$DESTDIR$sysconfdir/request-key.d/id_resolver.conf"
 install_symlink /etc/local/access.conf                    "$DESTDIR$sysconfdir/security/access.conf"
 install_data misc_etc_files/cups/client.conf              "$DESTDIR$sysconfdir/cups/client.conf"
+install_data misc_etc_files/systemd/system/basic.target.d/want-network.conf \
+                                                          "$DESTDIR$sysconfdir/systemd/system/basic.target.d/want-network.conf"
 
 postinstall
 exit

misc_etc_files/systemd/system/basic.target.d/want-network.conf

@@ -0,0 +1,4 @@
+[Unit]
+
+Wants=network.target
+After=network-online.target

misc_systemd_units/ip6.service

@@ -1,5 +1,7 @@
 [Unit]
 
+DefaultDependencies=no
+
 Wants=startup-tags.service
 After=startup-tags.service
 ConditionPathExists=/node/tags/ip6

misc_systemd_units/mxvlan.service

@@ -1,5 +1,7 @@
 [Unit]
 
+DefaultDependencies=no
+
 Wants=network.service
 After=network.service
 Before=network.target