build+face: Fixing regression that broke ethernet support

As of this commit, libpcap is required unless specifically disabled
using --without-libpcap parameter during configure stage.

Change-Id: Iec6f8bd9babfe4da193c98a49043b08319311106
Refs: #1472
diff --git a/tests/mgmt/face-manager.cpp b/tests/mgmt/face-manager.cpp
index c410878..e799944 100644
--- a/tests/mgmt/face-manager.cpp
+++ b/tests/mgmt/face-manager.cpp
@@ -653,7 +653,7 @@
                              "Unrecognized option \"hello\" in \"udp\" section"));
 }
 
-#ifdef HAVE_PCAP
+#ifdef HAVE_LIBPCAP
 
 BOOST_AUTO_TEST_CASE(TestProcessSectionEther)
 {