LP1920234: Manual carousels should link to the existing bucket, rather than creating...

LP1920234: Manual carousels should link to the existing bucket, rather than creating a duplicate one

Steps to test:
1. Create a record bucket
2. Add some records to it
3. Create a carousel from your bucket
4. In Local Administration > Carousel Library Mappings, set up your new bucket to display
in your library's public catalog.
5. Confirm that your records are displaying in the carousel.
6. Remove some records from your bucket, and add some new ones.
7. Refresh the public catalog in your browser, and note that the carousel contents have
updated according to the changes you made to your bucket.

Signed-off-by: Jane Sandberg <js7389@princeton.edu>
Signed-off-by: Terran McCanna <tmccanna@georgialibraries.org>
Signed-off-by: Stephanie Leary <stephanie.leary@equinoxoli.org>
Signed-off-by: Michele Morgan <mmorgan@noblenet.org>
Signed-off-by: blake <blake@mobiusconsortium.org>
Signed-off-by: Steven Mayo <smayo@georgialibraries.org>