PLT-6358: Server HTTP client improvements (#6980)

* restrict untrusted, internal http connections by default

* command test fix

* more test fixes

* change setting from toggle to whitelist

* requested ui changes

* add isdefault diagnostic

* fix tests

app/notification.go

@@ -682,7 +682,7 @@ func sendToPushProxy(msg model.PushNotification, session *model.Session) {
 
 	request, _ := http.NewRequest("POST", *utils.Cfg.EmailSettings.PushNotificationServer+model.API_URL_SUFFIX_V1+"/send_push", strings.NewReader(msg.ToJson()))
 
-	if resp, err := utils.HttpClient().Do(request); err != nil {
+	if resp, err := utils.HttpClient(true).Do(request); err != nil {
 		l4g.Error("Device push reported as error for UserId=%v SessionId=%v message=%v", session.UserId, session.Id, err.Error())
 	} else {
 		pushResponse := model.PushResponseFromJson(resp.Body)