test: Clear out old mocks prior to testing

This ensures we don't have stale mock data left over after each run
that will leak into unrelated tests.

Change-Id: I08bc12f99f1103c5d3024bf90047105b221622a2
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/test_rtnetlink.cpp b/test/test_rtnetlink.cpp
index 794a0dd..6a8c02d 100644
--- a/test/test_rtnetlink.cpp
+++ b/test/test_rtnetlink.cpp
@@ -87,6 +87,7 @@
 TEST_F(TestRtNetlink, WithSingleInterface)
 {
     using namespace std::chrono;
+    mock_clear();
     // Adds the following ip in the getifaddrs list.
     mock_addIF("igb5", 6);
     mock_addIP("igb5", "127.0.0.1", "255.255.255.128", IFF_UP | IFF_RUNNING);