Fix for failing test test_the_displayed_message_for_incompatible_complete_themes
- the page is opening with a hover card displayed, so added a step to clear hovercards
Fix test_searching_for_addon_type_returns_results_of_correct_type
- glow is no longer found, changed to nasa
Merge pull request #727 from bobsilverberg/fix_test_the_displayed_message_for_incompatible_complete_themes

Fix for failing test test_the_displayed_message_for_incompatible_complete_themes