Switching the tests to use ember admin by default

ref #3060

- Some of our tests use the old signin/signout as part of the setup/teardown process. The old stuff is going away, so this PR switches everything over to use the new admin by default.
- There wil be a further PR to remove the old stuff completely soon.
Merge pull request #3117 from ErisDS/switch-tests

Switching the tests to use ember admin by default