This PR contains three changes:
1. We will use spark.sql.warehouse.dir set warehouse location. We will not use hive.metastore.warehouse.dir.
2. SessionCatalog needs to set the location to default db. Otherwise, when creating a table in SparkSession without hive support, the default db's path will be an empty string.
3. When we create a database, we need to make the path qualified.
Existing tests and new tests
Author: Yin Huai <yhuai@databricks.com>
Closes#12812 from yhuai/warehouse.
0182d9599d