Bug 29993: Show Syndetics covers when using shelfbrowser controls

Bug 29993: Show Syndetics covers when using shelfbrowser controls

1. Have items that include itemcallnumber.
2. Enable OPACShelfBrowser.
3. Enable SyndeticsCoverImages and SyndeticsEnabled.
4. Go the an OPAC detail page and open the shelf browser.
5. Use the Next/Previous buttons.
6. Notice that no Syndetics images populate after using Next/Previous buttons.
7. Apply patch and try again, cover images for Syndetics should be generating.

Signed-off-by: Barbara Johnson <barbara.johnson@bedfordtx.gov>
Rebased-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>