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/controller.go

@@ -111,6 +111,7 @@ func (c *Controller) initOperatorConfig() {
 	}
 
 	c.opConfig = config.NewFromMap(configMapData)
+	c.warnOnDeprecatedOperatorParameters()
 
 	scalyrAPIKey := os.Getenv("SCALYR_API_KEY")
 	if scalyrAPIKey != "" {
@@ -119,6 +120,14 @@ func (c *Controller) initOperatorConfig() {
 
 }
 
+// warningOnDeprecatedParameters emits warnings upon finding deprecated parmaters
+func (c *Controller) warnOnDeprecatedOperatorParameters() {
+	if c.opConfig.EnableLoadBalancer != nil {
+		c.logger.Warningf("Operator configuration parameter 'enable_load_balancer' is deprecated and takes no effect. " +
+			"Consider using the 'enable_master_load_balancer' or 'enable_replica_load_balancer' instead.")
+	}
+}
+
 func (c *Controller) initPodServiceAccount() {
 
 	if c.opConfig.PodServiceAccountDefinition == "" {