SpecialSearch: Fix pagination

This basically reverts f4357b6 but fixes it while we're here. Requesting
one extra result causes extra load and weird queries against the search
backend...all to be thrown away. Plus it's showing "Results 1-21 of N"
when we're only showing 20 which is a regression.

All search backends implement getTotalHits() so use that count instead
to figure out if we're on the last page.

Change-Id: Ib38b1e124bea7133f48209ef8af1b1e26b4dba75
Merge "SpecialSearch: Fix pagination"