Do not use netns as ID or for entropy

ContainerID is now required so use that
or generate random bytes.

Fixes #5

scripts/docker-run.sh

@@ -9,10 +9,10 @@ contid=$(docker run -d --net=none busybox:latest /bin/sleep 10000000)
 pid=$(docker inspect -f '{{ .State.Pid }}' $contid)
 netnspath=/proc/$pid/ns/net
 
-./exec-plugins.sh add $netnspath
+./exec-plugins.sh add $contid $netnspath
 
 function cleanup() {
-	./exec-plugins.sh del $netnspath
+	./exec-plugins.sh del $contid $netnspath
 	docker kill $contid >/dev/null
 }
 trap cleanup EXIT