Fix selenium tests
Fix selenium tests

We were using /api/roles endpoint to retrieve the session cookie. This
worked because the GET request was redirected to the login page, but
now we return 403 on unauthorized GET requests.

The solution is to simply use the /login endpoint directly.

j0gurt/ggrc-core,selahssea/ggrc-core,selahssea/ggrc-core,j0gurt/ggrc-core,VinnieJohns/ggrc-core,andrei-karalionak/ggrc-core,plamut/ggrc-core,andrei-karalionak/ggrc-core,j0gurt/ggrc-core,plamut/ggrc-core,j0gurt/ggrc-core,josthkko/ggrc-core,AleksNeStu/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,AleksNeStu/ggrc-core,selahssea/ggrc-core,VinnieJohns/ggrc-core,andrei-karalionak/ggrc-core,AleksNeStu/ggrc-core,VinnieJohns/ggrc-core,andrei-karalionak/ggrc-core,josthkko/ggrc-core,josthkko/ggrc-core,VinnieJohns/ggrc-core