face: Fix bug with removePendingInterest

Change-Id: I364c1441da2cc0042ba461bc3a6cb4b70e53b166
Refs: #1917
diff --git a/src/face.cpp b/src/face.cpp
index 79d8dc1..42fc522 100644
--- a/src/face.cpp
+++ b/src/face.cpp
@@ -193,6 +193,12 @@
   m_ioService->post(bind(&Impl::asyncRemovePendingInterest, m_impl, pendingInterestId));
 }
 
+size_t
+Face::getNPendingInterests() const
+{
+  return m_impl->m_pendingInterestTable.size();
+}
+
 const RegisteredPrefixId*
 Face::setInterestFilter(const InterestFilter& interestFilter,
                         const OnInterest& onInterest,