Persist rp_filter=0 on every router interface (#539)

Effective rp_filter is max(all, <iface>). Setting `all`/`default` to 0 is not enough after a reboot: `/usr/lib/sysctl.d/50-redhat.conf` sets `net.ipv4.conf.*.rp_filter = 1`, which udev applies to every interface as it is created, so routed asymmetric traffic gets dropped once shorewall goes.

- add `net.ipv4.conf.*.rp_filter: 0` to the router role, overriding the vendor glob
- disable `enforce` for it, since `sysctl -n` cannot read glob keys

Reviewed-on: #539
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

hieradata/roles/infra/network/router.yaml

@@ -11,6 +11,10 @@ sysctl::base::values:
     value: '0'
   net.ipv4.conf.default.rp_filter:
     value: '0'
+  # overrides 50-redhat.conf's per-interface rp_filter=1 (applied by udev on link add); sysctl -n can't glob, so no enforce
+  net.ipv4.conf.*.rp_filter:
+    value: '0'
+    enforce: false
 
 # frrouting
 exporters::frr_exporter::enable: true