Bug 11328 - Show local cover images in staff client search results

Local cover images do not appear in staff client search results. This
patch adds them.

To test, enable the LocalCoverImages system preference and add at least
one cover image to a title. Perform a search which will return results
that include your title. Confirm that the local cover image is
displayed.

Search results should also display correctly with and without
AmazonCoverImages enabled as well as with LocalCoverImages disabled.

Signed-off-by: wajasu <matted-34813@mypacks.net>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 9ce9eea2dbb35be4f3f28314cb90f4edb624c31c)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>