Hive map-side join job sometimes fails with ROOT_INPUT_INIT_FAILURE

When Hive does a map-side join it can generate a DAG where a vertex has two inputs, one from an upstream task and another using MRInputAMSplitGenerator. If it takes a while for MRInputAMSplitGenerator to compute the splits and one of the tasks for the other upstream vertex completes then the job can fail with an error since MRInputAMSplitGenerator does not expect to receive any events.