Add Daemon restart test along with Daemon utils

This PR allows writing tests that need a daemon restart. It uses hack/dind.
There is also a very useful test case that can also serve as an example on how to use it.

Ping @unclejack @tianon @vieux
I don't like custom asserts. I believe that tests should be as verbose as it possible and I don't mind about more 5-6 lines in test :)