Bug 17048: Fix pagination offset for authority searches

Bug 17048: Fix pagination offset for authority searches

At the intranet, the pagination has been broken by bug 12478 (Elastic
Search). There was a confusion between the offset and the page number.

At the OPAC, it is broken since bug 2735 which has mimicked the intranet
script.

Test plan:
Search for a term which will return more than 1 page of results.
Click on the second page
=> Without this patch, the first result of the second page is the second
result of the first page
=> With this patch applied, the offset will be corrected

Signed-off-by: Aleisha Amohia <aleishaamohia@hotmail.com>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit bff08b9962318f6eca873693936e369456f428e5)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>