public void addEnv(Map<String, String> env){
    env.put(UserGroupInformation.HADOOP_TOKEN_FILE_LOCATION,
        tokenPath.toUri().getPath());
  }
SecureCmdDoAs - Helper class for setting parameters and env necessary for
being able to run child jvm as intended user.
Used only when kerberos security is used
ql/src/java/org/apache/hadoop/hive/ql/exec/SecureCmdDoAs.java