daemon: use asio::defer() instead of asio::post() where appropriate

Change-Id: I24d0fab6499d6430dd500ca157daa87f48960d15
diff --git a/tests/daemon/rib/fib-updates-common.hpp b/tests/daemon/rib/fib-updates-common.hpp
index 33b549d..15e623f 100644
--- a/tests/daemon/rib/fib-updates-common.hpp
+++ b/tests/daemon/rib/fib-updates-common.hpp
@@ -33,6 +33,8 @@
 #include "tests/daemon/global-io-fixture.hpp"
 #include "tests/daemon/rib/create-route.hpp"
 
+#include <boost/asio/defer.hpp>
+
 #include <ndn-cxx/util/dummy-client-face.hpp>
 
 namespace nfd::tests {
@@ -80,7 +82,7 @@
              uint32_t nTimeouts)
   {
     updates.push_back(update);
-    getGlobalIoService().post([=] {
+    boost::asio::defer(getGlobalIoService(), [=] {
       if (mockSuccess) {
         onUpdateSuccess(update, onSuccess, onFailure);
       }