mgmt: report face MTU in faces/list and faces/query datasets

This commit also contains an overall cleanup of FaceManager
and extends the FaceDataset test case.

Change-Id: I8c8290b0dc04b25582e66a5c6dad3cca4dd226eb
Refs: #4763, #3325
diff --git a/tests/daemon/mgmt/strategy-choice-manager.t.cpp b/tests/daemon/mgmt/strategy-choice-manager.t.cpp
index b4718a9..817966e 100644
--- a/tests/daemon/mgmt/strategy-choice-manager.t.cpp
+++ b/tests/daemon/mgmt/strategy-choice-manager.t.cpp
@@ -28,6 +28,7 @@
 
 #include "nfd-manager-common-fixture.hpp"
 #include "../fw/dummy-strategy.hpp"
+
 #include <ndn-cxx/mgmt/nfd/strategy-choice.hpp>
 
 namespace nfd {
@@ -204,7 +205,7 @@
     expected[entry.getPrefix()] = entry.getStrategyInstanceName();
   }
 
-  for (int i = expected.size(); i < 1024; ++i) {
+  for (size_t i = expected.size(); i < 1024; ++i) {
     Name name("/SC");
     name.appendNumber(i);
     Name strategy = DummyStrategy::getStrategyName(i);
@@ -214,7 +215,8 @@
     expected[name] = strategy;
   }
 
-  receiveInterest(Interest("/localhost/nfd/strategy-choice/list"));
+  receiveInterest(Interest("/localhost/nfd/strategy-choice/list").setCanBePrefix(true));
+
   Block dataset = concatenateResponses();
   dataset.parse();
   BOOST_CHECK_EQUAL(dataset.elements_size(), expected.size());