Driver.queryState.commandType is often not set correctly

For example, various EXPLAIN <....> operations all have this set to QUERY though it would make more sense to set it to HiveOperation.EXPLAIN especially since ExplainSemanticAnalyzer forks off another instance of Driver to run the <...> for EXPLAIN ANALYZE <...> types of commands but shares the QueryState between the 2.

Changing this of course causes a lot of .q.out files to change.

It would useful in general for the Driver to know the HiveOperation type more precisely.

For example, there is no distinction between SELECT/UPDATE/INSERT/DELETE/MERGE.

Need to clean this up.