Bug 1069810 - Homescreen application does not handle basic authentication in icon urls

Use the url string instead of an anchor element when fetching icons
Bug 1069810 - Add icon auth test r=kgrandon
Merge pull request #24225 from KevinGrandon/bug_1069810_home_screen_auth_fix_with_test

Bug 1069810 - Homescreen application does not handle basic authentication in icon urls