Hardcoded task ping timeout kills tasks localizing large amounts of data

When a task is launched and spends more than 5 minutes localizing files, the AM will kill the task due to ping timeout. The AM's TaskHeartbeatHandler currently tracks tasks via a progress timeout and a ping timeout. The progress timeout can be controlled via mapreduce.task.timeout and even disabled by setting the property to 0. The ping timeout, however, is hardcoded to 5 minutes and cannot be configured. Therefore if the task takes too long localizing, it never gets running in order to ping back to the AM and the AM kills it due to ping timeout.