Fix linter warnings in netd tests

Test: tests/runtests.sh
Change-Id: Id06480fa3c1fc04f5669c42b87b263b46bf614fd
diff --git a/server/TrafficController.cpp b/server/TrafficController.cpp
index 2d9e2d1..ffbc363 100644
--- a/server/TrafficController.cpp
+++ b/server/TrafficController.cpp
@@ -52,7 +52,7 @@
 #include "NetlinkListener.h"
 #include "qtaguid/qtaguid.h"
 
-using namespace android::bpf;
+using namespace android::bpf;  // NOLINT(google-build-using-namespace): grandfathered
 
 namespace android {
 namespace net {