function bindClient(client, bindDN, ldapPassword) {
  appLog.trace(`LDAP bind to ${bindDN}`);
  return new Promise((resolve, reject) => {
    client.bind(bindDN, ldapPassword, function (err) {
      if (err) {
        appLog.trace(err, 'LDAP bind error');
        return reject(err);
      }
      appLog.trace('LDAP bind success');
      return resolve();
    });
  });
}
Convenience wrapper to promisify client.bind() function
@param {*} client
@param {string} bindDN
@param {string} ldapPassword