basic regression test of runDockershim

- added basic regression test to ensure an error is raised in the
   case of an unconfigured runtime, and the case of asking for a docker
   runtime when compiled dockerless

Signed-off-by: Morgan Bauer <mbauer@us.ibm.com>

pkg/kubelet/kubelet_test.go

@@ -1953,6 +1953,13 @@ func TestSyncPodKillPod(t *testing.T) {
 	checkPodStatus(t, kl, pod, v1.PodFailed)
 }
 
+func TestPreInitRuntimeService(t *testing.T) {
+	err := PreInitRuntimeService(nil, nil, nil, "", "", "", "", "")
+	if err == nil {
+		t.Fatal("PreInitRuntimeService should fail when not configured with a container runtime")
+	}
+}
+
 func waitForVolumeUnmount(
 	volumeManager kubeletvolume.VolumeManager,
 	pod *v1.Pod) error {