xenapi: upload/download params consistency change

This patch updates the params for upload_image and download_image to be
consistent.

Change-Id: Ie6dbdb096624fb06a4fc29a461c3569e48df3ec0
Partial-Bug: 1380776
DB API: Pass columns_to_join to instance_get_active_by_window_joined

This makes the instance_get_active_by_window_joined database API
configurable for which columns should be joined from other tables,
similar to instance_get_all.

This lays the groundwork for the Instance object to pass expected_attrs
to the DB API for filtering which columns to load.

Partial-Bug: #1383469

Change-Id: I7089d732cbd06a854d47b7b9e4faf21b9ef498f1
Merge "xenapi: upload/download params consistency change"
Merge "DB API: Pass columns_to_join to instance_get_active_by_window_joined"