Bug 21405: Fix authorities pagination for Zebra and ES

Bug 21405: Fix authorities pagination for Zebra and ES

Bug 20261 introduced an error because search_auth_compat responded
differently for ES and Zebra, now bug 19365 fixed the underlying
difference. This patch restores previous code to fix pagination.

Additionally we add a fix for 10000+ results in ES and remove a double
import of C4::Auth

To test:
 1 - Perform an authorities search with 1+ pages using Zebra
 2 - Page through results, note you are only offseeting by 1 each time
 3 - Perform an authorities search with 10,000+ results in ES
 4 - Click on the last page and get an error
 5 - Apply patch
 6 - Retry Zebra search
 7 - Results should paginate correctly
 8 - Clicking on last page should return last results
 9 - Retry ES results
10 - Results should paginate correct
11 - Clicking on last page should return last results

Signed-off-by: Ere Maijala <ere.maijala@helsinki.fi>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>