Timecop is freezing tests

We are using https://github.com/matteodepalo/ember-cli-timecop in a few component integration tests and until now this worked fine. We tried to convert those tests to use the new testing APIs, but now `Timecop.freeze()` seems to block the `async render(...)` call from continuing.

An issue similar to this has existed in the past where Backburner.js would not continue running when `Date.now()` is mocked and frozen, but was fixed by getting a reference to the `Date` object on startup and then using that reference instead of the temporary mocked global.