Change {win7,linux}_firefox to release version 22

This changes the firefox version to the current release
(22). Unfortunately, sauce does not provide osx/22, so did not update
that. It also changes s/Windows 2008/Window 7/; the documented versions
have changed (again), but the name change is moot since you will get the
same VM by either name.

With this change, I don't have different failure rates with running the
tests.