Deprecate old LB options, fix endpoint sync. (#287)

* Depreate old LB options, fix endpoint sync.

- deprecate useLoadBalancer, replicaLoadBalancer from the manifest
  and enable_load_balancer from the operator configuration. The old
  operator configuration options become no-op with this commit. For
  the old manifest options, `useLoadBalancer` and `replicaLoadBalancer`
  are still consulted,  but only in the absense of the new ones
  (enableMasterLoadBalancer and enableReplicaLoadBalancer).

- Make sure the endpoint being created during the sync receives proper
  addresses subset. This is more critical for the replicas, as for the
  masters Patroni will normally re-create the endpoint before the
  operator.

- Avoid creating the replica endpoint, since it will be created automatically
  by the corresponding service.
- Update the README and unit tests.

Code review by @mgomezch and @zerg-junior

pkg/controller/postgresql_test.go

@@ -0,0 +1,43 @@
+package controller
+
+import (
+	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+	"reflect"
+	"testing"
+)
+
+var (
+	True  bool = true
+	False bool = false
+)
+
+func TestMergeDeprecatedPostgreSQLSpecParameters(t *testing.T) {
+	c := NewController(&spec.ControllerConfig{})
+
+	tests := []struct {
+		name  string
+		in    *spec.PostgresSpec
+		out   *spec.PostgresSpec
+		error string
+	}{
+		{
+			"Check that old parameters propagate values to the new ones",
+			&spec.PostgresSpec{UseLoadBalancer: &True, ReplicaLoadBalancer: &True},
+			&spec.PostgresSpec{UseLoadBalancer: &True, ReplicaLoadBalancer: &True,
+				EnableMasterLoadBalancer: &True, EnableReplicaLoadBalancer: &True},
+			"New parameters should be set from the values of old ones",
+		},
+		{
+			"Check that new parameters are not set when both old and new ones are present",
+			&spec.PostgresSpec{UseLoadBalancer: &True, EnableReplicaLoadBalancer: &True},
+			&spec.PostgresSpec{UseLoadBalancer: &True, EnableReplicaLoadBalancer: &True},
+			"New parameters should remain unchanged when both old and new are present",
+		},
+	}
+	for _, tt := range tests {
+		result := c.mergeDeprecatedPostgreSQLSpecParameters(tt.in)
+		if !reflect.DeepEqual(result, tt.out) {
+			t.Errorf("%s: %v", tt.name, tt.error)
+		}
+	}
+}