fw4: fall back to device if l3_device is not available in ifstatus

fw4: fall back to device if l3_device is not available in ifstatus

If the l3_device ifstatus property of a referenced logical interface is
unavailable, e.g. due to the logical interface being down, no jump rules
to the related zone chains are emitted. This is a deviation from fw3 which
fell back to the l2 device value in this case.

Do the same in firewall4 to still produce matching rules in the majority
of cases, even if the l3 device ends up being something else.

Fixes: #10639
Signed-off-by: Jo-Philipp Wich <jo@mein.io>