yangerd: Follow force_forwarding for IPv6 routing interfaces

confd sets force_forwarding for IPv6, the aggregator reads it, but only
the plain forwarding file was watched.  An IPv6-only change was picked
up solely because the IPv4 sysctl is written at the same time.

Signed-off-by: Mattias Walström <[email protected]>

Author: mattiaswal

src/yangerd/cmd/yangerd/main.go

@@ -227,6 +227,7 @@ func main() {
 	forwardingPaths := []string{
 		"/proc/sys/net/ipv4/conf/*/forwarding",
 		"/proc/sys/net/ipv6/conf/*/forwarding",
+		"/proc/sys/net/ipv6/conf/*/force_forwarding",
 	}
 	forwarding := fswatcher.WatchHandler{
 		TreeKey:  routingTreeKey,