/**
  * Upates an existing persistent record
  *
  * @param  Tinebase_Record_Interface  $_contact
  * 
  * @return Tinebase_Record_Interface|NULL
  */
 public function update(Tinebase_Record_Interface $_record)
 {
     $allData = $_record->toArray();
     $samAccount = new Tinebase_Model_SAMUser($allData, true);
     $samAccount->acctFlags = '[W          ]';
     $posixAccount = new Tinebase_Model_FullUser($allData, true);
     $posixAccount->sambaSAM = $samAccount;
     $posixAccount = $this->_ldap->updateUserInSyncBackend($posixAccount);
     return $this->get($posixAccount->getId());
 }