## What changes were proposed in this pull request?

it's weird that every session can set its own warehouse path at runtime, we should forbid it and make it a static conf.

## How was this patch tested?

existing tests.

Author: Wenchen Fan <wenchen@databricks.com>

Closes #15825 from cloud-fan/warehouse.

(cherry picked from commit 4ac9759f)
Signed-off-by: Reynold Xin <rxin@databricks.com>