Improve behavior on node decomissionining (#184)

* Trigger the node migration on the lack of  the readiness label.

* Examine the node's readiness status on node add.

Make sure we don't miss the not ready node, especially when the
operator is killed during the migration.

pkg/controller/node_test.go

@@ -0,0 +1,65 @@
+package controller
+
+import (
+	"testing"
+
+	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/pkg/api/v1"
+)
+
+const (
+	readyLabel = "lifecycle-status"
+	readyValue = "ready"
+)
+
+func initializeController() *Controller {
+	var c = NewController(&spec.ControllerConfig{})
+	c.opConfig.NodeReadinessLabel = map[string]string{readyLabel: readyValue}
+	return c
+}
+
+func makeNode(labels map[string]string, isSchedulable bool) *v1.Node {
+	return &v1.Node{
+		ObjectMeta: metav1.ObjectMeta{
+			Namespace: v1.NamespaceDefault,
+			Labels:    labels,
+		},
+		Spec: v1.NodeSpec{
+			Unschedulable: !isSchedulable,
+		},
+	}
+}
+
+var c = initializeController()
+
+func TestNodeIsReady(t *testing.T) {
+	testName := "TestNodeIsReady"
+	var testTable = []struct {
+		in  *v1.Node
+		out bool
+	}{
+		{
+			in:  makeNode(map[string]string{"foo": "bar"}, true),
+			out: true,
+		},
+		{
+			in:  makeNode(map[string]string{"foo": "bar"}, false),
+			out: false,
+		},
+		{
+			in:  makeNode(map[string]string{readyLabel: readyValue}, false),
+			out: true,
+		},
+		{
+			in:  makeNode(map[string]string{"foo": "bar", "master": "true"}, false),
+			out: true,
+		},
+	}
+	for _, tt := range testTable {
+		if isReady := c.nodeIsReady(tt.in); isReady != tt.out {
+			t.Errorf("%s: expected response %t doesn't match the actual %t for the node %#v",
+				testName, tt.out, isReady, tt.in)
+		}
+	}
+}