Repair sample-client after ->bytes rewrites.

sample-client.scm

@@ -24,7 +24,9 @@
 
 (define (run sock msg)
   (define resp (make-bytevector 512))
-  (send sock (dns-message->bytes msg))
+  ;; TODO pack bytevector here
+  (send sock (call-with-values (lambda () ((dns-message->bytes msg) (make-bytevector 100) 0))
+               (lambda (_ bv ptr) bv)))
   (recv! sock resp)
   (call-with-values (lambda () ((bytes->dns-message resp) 0))
     (lambda (resp _) resp)))