Hive communicates state from RecordReader to Processor via JobConf

Hive currently switches between operator pipelines + partition descriptors via a map.input.file

In the CombineFileInputFormat case Hive relies on the fact that CombineFileRecordReader sets this field every time a new file is processed. This file will then be read in the processor to setup the correct processing pipeline.

After the Tez refactor RecordReader and TezProcessor use different job conf instances. Because of that Hive will fail since map.input.file isn't set and updated in the processor's conf.