crypto: set data before sending to thread pool

fixes test-crypto

src/node_crypto.cc

@@ -3878,8 +3878,8 @@ PBKDF2(const Arguments& args) {
   request->callback = Persistent<Function>::New(callback);
 
   uv_work_t* req = new uv_work_t();
-  uv_queue_work(uv_default_loop(), req, EIO_PBKDF2, EIO_PBKDF2After);
   req->data = request;
+  uv_queue_work(uv_default_loop(), req, EIO_PBKDF2, EIO_PBKDF2After);
 
   return Undefined();
 }