LP#1976002: Include ancestors in item location filters

LP#1976002: Include ancestors in item location filters

The item location selector should include locations from ancestor org
units regardless of the specific permission-limiting check it may be
asked to perform.  Item locations at ancestor org units are valid for
use on items in descendant locations.

This commit also makes the org filter list unique.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Andrea Buntz Neiman <abneiman@equinoxOLI.org>
Signed-off-by: Jane Sandberg <sandbergja@gmail.com>