New unit-test for dataflow_output_id under various conditions

Created by: muffato

This is a request for comments. I've tried to compile a list of all possible dataflow_output_id calls, with the expected behaviour from Hive. At the moment, the test doesn't pass on 2.4 (neither it does on master), but I've got a couple of commits ready, assuming these below are the expected outcomes.

There is a case where I really don't know what's more "natural". If the template needs a_multiplier and a_multiplier is set to 9650156169 in the input_id, but to 27 in the parameter hash (the parameter has been modified at runtime). Which value should be used in the dataflow ??