Revert accidental deletion of allocator creation.

Signed-off-by: Steve Wolter <swolter@google.com>

Author: stevewolter

rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp

@@ -60,6 +60,7 @@ NodeParameters::NodeParameters(
   // TODO(wjwwood): expose this allocator through the Parameter interface.
   rclcpp::PublisherOptionsWithAllocator<AllocatorT> publisher_options(
     parameter_event_publisher_options);
+  publisher_options.allocator = std::make_shared<AllocatorT>();
 
   if (start_parameter_services) {
     parameter_service_ = std::make_shared<ParameterService>(node_base, node_services, this);

rclcpp/test/rclcpp/test_subscription.cpp

@@ -247,6 +247,7 @@ TEST_F(TestSubscription, various_creation_signatures) {
   }
   {
     rclcpp::SubscriptionOptionsWithAllocator<std::allocator<void>> options;
+    options.allocator = std::make_shared<std::allocator<void>>();
     EXPECT_NE(nullptr, options.get_allocator());
     auto sub = rclcpp::create_subscription<Empty>(
       node, "topic", 42, cb, options);