Order network@if.service before network-online.target

Units, that need network to be present, normally are expected to use
After=network-online.target. This does not work on shutdown currently
because network@if.service itself does not have any dependency on
network-online.target and is stopped too early.  Most obvious case is
NFS/CIFS mounts in /etc/fstab. Adding ordering dependency against
network-online.target ensures it is stopped only after all other services
are stopped.

Fixes bnc#857031

Signed-off-by: Andrey Borzenkov <arvidjaar@gmail.com>
Updated changes for 13.1, obs submit rq#221976
ifup: do not redirect to systemd for ppp (bnc#846361)
updated changes (obs maintenance request #225402)