Eng 6436 distinct reroute

This is the fast, simple but not the best efficient solution for DISTINCT with GROUP BY cases. We will create tickets to optimize it later.
Remove this test and the m_hasPartitionColumnInDistinctGroupby member if we are not going to use it -- right now, it is only used to set a local variable that gets reset to false 2 lines later. Consider hard-coding the use of m_parsedSelect.m_groupByColumns in isPartitionColumnInGroupbyList.