core: when creating an activating busname attach all metadata fields to the messages queued for it

This way we can be sure that the service the messages are ultimately
intended for finds all fields it might need.

src/libsystemd/sd-bus/bus-kernel.c

@@ -1422,6 +1422,7 @@ int bus_kernel_create_starter(const char *bus, const char *name, bool accept_fd,
         hello->size = size;
         hello->conn_flags = KDBUS_HELLO_ACTIVATOR | (accept_fd ? KDBUS_HELLO_ACCEPT_FD : 0);
         hello->pool_size = KDBUS_POOL_SIZE;
+        hello->attach_flags = _KDBUS_ATTACH_ALL;
 
         if (ioctl(fd, KDBUS_CMD_HELLO, hello) < 0) {
                 safe_close(fd);