public void login(String fileConfKey, String principalConfKey) throws IOException {
    User.login(getConf().get(fileConfKey), getConf().get(principalConfKey));
  }
Login with given keytab and principal. This can be used for both SPN(Service Principal Name)
and UPN(User Principal Name) which format should be clientname@REALM.
@param fileConfKey      config name for client keytab
@param principalConfKey config name for client principal
@throws IOException underlying exception from UserGroupInformation.loginUserFromKeytab
hbase-common/src/main/java/org/apache/hadoop/hbase/security/UserProvider.java