#422 combiner->command_complete_count needs to be handled correct

[Amit Khandekar]

There seem to be some issue with combiner->command_complete_count. Currently it checks for consistency of number of tuples returned for replicated tables, but it does that only for FQS. Need to completely remove the dependency on whether it's an FQS or non-FQS DML query. For this, command_complete_count needs to be better handled. Currently this field is being updated for each iteration of FetchTuple by re-using the same combiner for each iteration, whereas it seems it should be updated only for each node execution, not for each tuple fetched.