Stop deleting DaemonSet pods during drain.

We do this because they will be recreated immediately by the
DaemonSet Controller.  In addition, we also require a specific flag
(--ignore-daemonsets) when there are DaemonSet pods on the node.

pkg/kubectl/cmd/drain_test.go

@@ -323,8 +323,18 @@ func TestDrain(t *testing.T) {
 			pods:         []api.Pod{ds_pod},
 			rcs:          []api.ReplicationController{rc},
 			args:         []string{"node"},
+			expectFatal:  true,
+			expectDelete: false,
+		},
+		{
+			description:  "DS-managed pod with --ignore-daemonsets",
+			node:         node,
+			expected:     cordoned_node,
+			pods:         []api.Pod{ds_pod},
+			rcs:          []api.ReplicationController{rc},
+			args:         []string{"node", "--ignore-daemonsets"},
 			expectFatal:  false,
-			expectDelete: true,
+			expectDelete: false,
 		},
 		{
 			description:  "Job-managed pod",