UI Tasks view: fix per page settings

Configuration -> Tasks -> per page settings and page navigation
wouldn't work correctly:
* the view would always default to 50 items per page
* incorrect numbers shown next to the navigation icons

Fixes #818

https://bugzilla.redhat.com/show_bug.cgi?id=1171150
@mzazrivec your analysis above is correct, the question here is should we leave it as it is currently working or do we need to figure out a way to change the path so paging controls send up a transaction to index method. @AparnaKarve @dclarizio thoughts?