hadoop-compat/src/main/java/com/twitter/elephantbird/util/HadoopCompat.java
public static TaskAttemptContext newTaskAttemptContext(
                            Configuration conf, TaskAttemptID taskAttemptId) {
    return (TaskAttemptContext)
        newInstance(TASK_CONTEXT_CONSTRUCTOR, conf, taskAttemptId);
  }
public static TaskAttemptContext newTaskAttemptContext(
                            Configuration conf, TaskAttemptID taskAttemptId) {
    return (TaskAttemptContext)
        newInstance(TASK_CONTEXT_CONSTRUCTOR, conf, taskAttemptId);
  }
Creates TaskAttempContext from a JobConf and jobId using the correct
constructor for based on Hadoop version.