Improved handling of probelm causes and better error messages when connecting to HDFS for hdfs resident files.

Added HDFS as dependency to pact-client, to allow local-executor to access hdfs files.
Fix1: Combiner gets same DOP and SubtasksPerInstance as its input to be chainable
Fix2: Local strategy of stand-alone (non-chained) combine driver
      Adapted CombineTask tests to new local strategy
Fixed instantiation of utility combine node to use the correct properties.