These code paths usually work, but are randomly failing in Node 8 environments since we updated to NaN 2.14.0. We're going to skip these tests on Node 8, because the diagnosis is very tricky.

For the 3 rebase tests, as far as I can tell, they:
1. Get to rebase.commit
2. The signingCb gets called and completed
3. Freeze
4. The tests timeout
5. rebase.commit finishes executing and the rest of the promise chain completes.

Increasing the timeout did not help, and exhibited the same behavior, strangely enough.