tests: add FreshnessPeriod where MustBeFresh is used

Also, set MustBeFresh in autoconfig-server HubData test,
to reflect the behavior of autoconfig client.

refs #4913

Change-Id: I0af29378630a2208e98ef0913d83668a603e9a88
diff --git a/tests/tools/ndn-autoconfig/multicast-discovery.t.cpp b/tests/tools/ndn-autoconfig/multicast-discovery.t.cpp
index 62d8bf1..0834bf5 100644
--- a/tests/tools/ndn-autoconfig/multicast-discovery.t.cpp
+++ b/tests/tools/ndn-autoconfig/multicast-discovery.t.cpp
@@ -100,6 +100,7 @@
     if (interest.getName() == "/localhop/ndn-autoconf/hub") {
       const char FACEURI[] = "udp://router.example.net";
       auto data = makeData(Name("/localhop/ndn-autoconf/hub").appendVersion());
+      data->setFreshnessPeriod(1_s);
       data->setContent(makeBinaryBlock(tlv::nfd::Uri, FACEURI, ::strlen(FACEURI)));
       face.receive(*data);
       return;