Bad table name on master_create_distributed_table()

This fix handles when master_create_distributed_table is called with
a an index as the first argument. More generally, it is called with
a relation that is not ordinary table or foreign table.

closes #13 
Same comment here as above. We could move this above as declaration. We then move the call to get_attnum which sets partitionColumnId to line 87 where it is used.