ffh.mesh_wireguard: fix [email protected]

On some supernodes, this did not work on system boot. The vx-* 
interfaces were added to batman but directly removed again. This was 
because the interfaces were not up. Now we set them up before the vx-* 
is added to batman.

Discussed in #147.

#147 (comment)

roles/ffh.mesh_wireguard/templates/addtobatX.j2

@@ -3,6 +3,7 @@ After=sys-subsystem-net-devices-{{ vxlan_iface_prefix }}\x2d%i.device
 
 [Service]
 Type=oneshot
+ExecStart=/sbin/ip link set {{ vxlan_iface_prefix }}-%i up
 ExecStart=/bin/sh /usr/bin/wait_for_iface.sh {{ vxlan_iface_prefix }}-%i unknown_is_fine
 ExecStart=/usr/sbin/batctl meshif bat%I if add {{ vxlan_iface_prefix }}-%i