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_vlan_interface.cpp b/test/test_vlan_interface.cpp
index 0ff893c..1dffc7e 100644
--- a/test/test_vlan_interface.cpp
+++ b/test/test_vlan_interface.cpp
@@ -48,6 +48,7 @@
     static EthernetInterface makeInterface(sdbusplus::bus::bus& bus,
                                            MockManager& manager)
     {
+        mock_clear();
         mock_addIF("test0", 1);
         return {bus, "/xyz/openbmc_test/network/test0", false, manager};
     }