fw: increment nOutNacks when sending a Nack from onInterestLoop

Also expand test coverage of all forwarder counters

Change-Id: I6948af05aca1b5589e2f1c8a1f23c002d39d0ec0
diff --git a/daemon/fw/forwarder.cpp b/daemon/fw/forwarder.cpp
index 131b4f1..ff21ee7 100644
--- a/daemon/fw/forwarder.cpp
+++ b/daemon/fw/forwarder.cpp
@@ -183,6 +183,7 @@
   lp::Nack nack(interest);
   nack.setReason(lp::NackReason::DUPLICATE);
   ingress.face.sendNack(nack);
+  ++m_counters.nOutNacks;
 }
 
 void
@@ -271,6 +272,7 @@
   // send Interest
   egress.sendInterest(interest);
   ++m_counters.nOutInterests;
+
   return &*it;
 }