public static void loginClient(Configuration conf, String keytabFileKey, String userNameKey,
    String hostname) throws IOException {
    login(conf, keytabFileKey, userNameKey, hostname, ZooKeeperSaslClient.LOGIN_CONTEXT_NAME_KEY,
      JaasConfiguration.CLIENT_KEYTAB_KERBEROS_CONFIG_NAME);
  }
Log in the current zookeeper client using the given configuration keys for the credential file
and login principal.
<p>
<strong>This is only applicable when running on secure hbase</strong> On regular HBase (without
security features), this will safely be ignored.
</p>
@param conf          The configuration data to use
@param keytabFileKey Property key used to configure the path to the credential file
@param userNameKey   Property key used to configure the login principal
@param hostname      Current hostname to use in any credentials
@throws IOException underlying exception from SecurityUtil.login() call
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKAuthentication.java