Give simple MJ bigger priority than bucketized ones

from the code it seems "standard" mapjoin is one of the last one tried; in case the table estimated to be bucketed in to 2 - but it's small ; Hive willl do a bucketmapjoin or dphj...even thru a simple mapjoin could have been an alternative...
https://github.com/apache/hive/blob/154ca3e3b5eb78cd49a4b3650c750ca731fba7da/ql/src/java/org/apache/hadoop/hive/ql/optimizer/ConvertJoinMapJoin.java#L157