Fix compilation after namespace change in ndn-cxx

refs: #2951

Change-Id: Ia9f3caee4733e7f137b5f6f22f7e154069b37f69
diff --git a/tests/publisher/test-segment-publisher.cpp b/tests/publisher/test-segment-publisher.cpp
index 0855466..7f34747 100644
--- a/tests/publisher/test-segment-publisher.cpp
+++ b/tests/publisher/test-segment-publisher.cpp
@@ -74,7 +74,7 @@
     size_t totalLength = 0;
     for (int64_t i = 0; i < N; i++)
       {
-        totalLength += ndn::prependNonNegativeIntegerBlock(outBuffer, ndn::tlv::Content, i);
+        totalLength += prependNonNegativeIntegerBlock(outBuffer, ndn::tlv::Content, i);
       }
     m_totalPayloadLength += totalLength;
     return totalLength;