luci-app-firewall: further luci-rpc/getHostHints compatibility fixes

Rework some further code instances to fall back to the legacy ipv4/ipv6
properties if needed.

Fixes: c7b7b42c

 ("treewide: Update JS using luci-rpc getHostHints")
Signed-off-by: Jo-Philipp Wich <jo@mein.io>