fix a another similar confusion on my part

src/foreign/from_cache_esi_deliver.c

@@ -176,9 +176,7 @@ vped_gzgz_init(struct req *req, void **priv)
  * _toparent vdp on the same request, rather than one request up as in the
  * original code.
  *
- * thus our VDP_bytes all have to flush
- *
- * XXX revisit maybe...
+ * thus we need to flush at the end of each call
  */
 static int v_matchproto_(vdp_bytes_f)
 vped_gzgz_bytes(struct req *req, enum vdp_action act, void **priv,
@@ -220,7 +218,7 @@ vped_gzgz_bytes(struct req *req, enum vdp_action act, void **priv,
 		/* Remove the "LAST" bit */
 		foo->dbits[0] = *pp;
 		foo->dbits[0] &= ~(1U << (foo->last & 7));
-		if (VDP_bytes(req, VDP_FLUSH, foo->dbits, 1))
+		if (VDP_bytes(req, VDP_NULL, foo->dbits, 1))
 			return (-1);
 		foo->ll++;
 		len--;
@@ -294,7 +292,7 @@ vped_gzgz_bytes(struct req *req, enum vdp_action act, void **priv,
 		default:
 			WRONG("compiler must be broken");
 		}
-		if (VDP_bytes(req, VDP_FLUSH, foo->dbits + 1, foo->lpad))
+		if (VDP_bytes(req, VDP_NULL, foo->dbits + 1, foo->lpad))
 			return (-1);
 	}
 	if (len > 0) {
@@ -315,7 +313,7 @@ vped_gzgz_bytes(struct req *req, enum vdp_action act, void **priv,
 		}
 	}
 	assert(len == 0);
-	return (0);
+	return (VDP_bytes(req, VDP_FLUSH, NULL, 0));
 }
 
 static int v_matchproto_(vdp_fini_f)