setup: enable systemd-networkd via preset for archlinux

setup: enable systemd-networkd via preset for archlinux

Note that this is now done in `setup_init` which is a
pre-start hook rather than a one time template fixup,
however, the presets are only applied on first boot or if
the user requests them explicitly, and the usual mechanisms
to prevent the file from being written can be used.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
(cherry picked from commit 454ea3918e70c7c0f82712c5bf1a6c2115e033f1)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>