text: Title:  get_table_names() returns incorrect list of table names when querying Spark SQL Thriftserver
  Body: Hi,
  I found out that the method `get_table_names()` in class HiveDialect in sqlalchemy_hive.py does not return correct names of tables. The result of query `show tables` are 3-tuples in the form `(schema_name , table_name , isTemporary)`. You need to get index 1 for `table_names`, but you get index 0. So it returns a list of duplicates of the `schema_name`.
  What can we do to fix this?