dyndns: run as a task

this lets us display logs

src/taskworker.js

@@ -9,6 +9,7 @@ const apptask = require('./apptask.js'),
     cloudron = require('./cloudron.js'),
     database = require('./database.js'),
     dns = require('./dns.js'),
+    dyndns = require('./dyndns.js'),
     externalLdap = require('./externalldap.js'),
     fs = require('fs'),
     mail = require('./mail.js'),
@@ -29,6 +30,7 @@ const TASKS = { // indexed by task type
     syncExternalLdap: externalLdap.sync,
     changeMailLocation: mail.changeLocation,
     syncDnsRecords: dns.syncDnsRecords,
+    syncDyndns: dyndns.sync,
     updateDiskUsage: system.updateDiskUsage,
 
     _identity: async (arg, progressCallback) => { progressCallback(); return arg; },