In some conditions, pages were skipped. This was implemented in the past
in f490a8d, but then reverted in 04ec543, because sometimes it was stuck
reloading the first page.
The code that loads more results was simplified and a lot of duplicate
code was removed. The logic to remove users who changed their vote was
also introduced again, but just for the regular polls.
Partially revert f490a8d39a because we aren't able to
load more than the initially preloaded voters.
We were always trying to load the 1st page of voters.
Also removed the "remove users who changed their vote" logic as it was not properly working in multiple choices polls.
cc @nbianca
* FIX: Fetch last page again if incomplete
The next fetched page number used to increase continuously even if the
last page was incomplete and fetching it again could have new voters.
* FIX: Do not display twice a user who changed vote
A user could appear under two voting options when they changed their
vote because pressing the Load More Voters button updated only the
current option.
