per_page does not work correctly in roles switcher on host edit page
Steps to reproduce:
1) have 20+ ansible roles in foreman
2) go to host edit page
3) notice per_page is set to 20 in roles switcher, but only 10 roles are actually in the list
4) change per_page to 5 - there will be 5 roles in the list, but per_page still shows 20. Also pagination shows '1-20 of x' and when requesting the next page, it fetches 5 roles, but still operates on the page size of 20 ('21-40 of x') and roles 6 - 15 are skipped and never displayed.