external ldap: run syncer every 4 hours

hardcoded for now but we should make this configurable

src/externalldap.js

@@ -18,6 +18,7 @@ const assert = require('assert'),
     AuditSource = require('./auditsource.js'),
     BoxError = require('./boxerror.js'),
     constants = require('./constants.js'),
+    cron = require('./cron.js'),
     debug = require('debug')('box:externalldap'),
     eventlog = require('./eventlog.js'),
     groups = require('./groups.js'),
@@ -87,6 +88,8 @@ async function setConfig(newConfig, auditSource) {
     if (newConfig.provider === 'noop') await users.resetSource(); // otherwise, the owner could be 'ldap' source and lock themselves out
 
     await eventlog.add(eventlog.ACTION_EXTERNAL_LDAP_CONFIGURE, auditSource, { oldConfig: removePrivateFields(currentConfig), config: removePrivateFields(newConfig) });
+
+    await cron.handleExternalLdapChanged();
 }
 
 // performs service bind if required