nspawn: fix DeviceAllow list

Commit 864e17068 ("nspawn: actually allow access to /dev/net/tun in the
container") added "/dev/net/tun" to the list of allowed devices but forgot
to tweak the array length, which caused "/dev/kdbus/*" to be missed.

src/nspawn/nspawn.c

@@ -1545,7 +1545,7 @@ static int register_machine(pid_t pid, int local_ifindex) {
                         return r;
                 }
 
-                r = sd_bus_message_append(m, "(sv)", "DeviceAllow", "a(ss)", 10,
+                r = sd_bus_message_append(m, "(sv)", "DeviceAllow", "a(ss)", 11,
                                           /* Allow the container to
                                            * access and create the API
                                            * device nodes, so that