BUG/MINOR: namespace: missing free in netns_sig_stop()

On soft-stop, netns_sig_stop() function is called to purge the shared
namespace tree by iterating over each entries to free them.

However, once an entry is cleaned up and removed from the tree, the entry
itself isn't freed and this results into a minor leak when soft-stopping
because entry was allocated using calloc() in netns_store_insert() when
parsing the configuration.

This could be backported in every stable versions.

src/namespace.c

@@ -54,6 +54,7 @@ static void netns_sig_stop(struct sig_handler *sh)
 		entry = container_of(node, struct netns_entry, node);
 		free(entry->node.key);
 		close(entry->fd);
+		free(entry);
 		node = next;
 	}
 }