MM tables - Tez merge may not run

If mm_all test is executed on MiniLlap, all the merge test cases pass but with changed order of rows; however, one can see in stats_mm, etc cases that while the stats are correct, the number of files changes. Seems like merge doesn't work in this case where it worked before. It's not pertinent to stats cases but it should be examined. Perhaps stats output for the # of files should be added to merge cases to make sure merge actually merges.