refactor restarting instances (#1535)

* refactor restarting instances and reduce listPods calls
* only add parameters to set if it differs from effective config
* update e2e test for updating Postgres config
* patch config only once

pkg/util/patroni/patroni.go

@@ -32,6 +32,7 @@ type Interface interface {
 	GetMemberData(server *v1.Pod) (MemberData, error)
 	Restart(server *v1.Pod) error
 	GetConfig(server *v1.Pod) (map[string]interface{}, error)
+	SetConfig(server *v1.Pod, config map[string]interface{}) error
 }
 
 // Patroni API client
@@ -163,6 +164,20 @@ func (p *Patroni) SetPostgresParameters(server *v1.Pod, parameters map[string]st
 	return p.httpPostOrPatch(http.MethodPatch, apiURLString+configPath, buf)
 }
 
+//SetConfig sets Patroni options via Patroni patch API call.
+func (p *Patroni) SetConfig(server *v1.Pod, config map[string]interface{}) error {
+	buf := &bytes.Buffer{}
+	err := json.NewEncoder(buf).Encode(config)
+	if err != nil {
+		return fmt.Errorf("could not encode json: %v", err)
+	}
+	apiURLString, err := apiURL(server)
+	if err != nil {
+		return err
+	}
+	return p.httpPostOrPatch(http.MethodPatch, apiURLString+configPath, buf)
+}
+
 // MemberDataPatroni child element
 type MemberDataPatroni struct {
 	Version string `json:"version"`