tests: Add a cleanup for the CNM tests

The CNM test was missing a cleanup which was handled earlier
with the CNI tests.

Signed-off-by: Archana Shinde <archana.m.shinde@intel.com>

virtcontainers/api_test.go

@@ -1358,6 +1358,8 @@ func TestStartStopSandboxHyperstartAgentSuccessfulWithCNMNetwork(t *testing.T) {
 		t.Skip(testDisabledAsNonRoot)
 	}
 
+	cleanUp()
+
 	config := newTestSandboxConfigHyperstartAgentCNMNetwork()
 
 	sockDir, err := testGenerateCCProxySockDir()