Add wait for changing display name, change edit page inheritance

This is to attempt to solve the intermittent failures on saucelabs jobs by adding a wait. It also fixes inconsistencies with which page model is used in checks as well as changes inheritance of edit page to inherit from base. @bobsilverberg r?
Just a cursory glance at the code, however this seems odd to add a wait to the test itself. Can it be moved to the page class?