MPI restart tests occasionally hang

[Sbozzolo]

The tests for restarts are a little different than most other tests: they run multiple simulations in the same MPI context. For reasons that I don't understand, this leads to the test hanging something. I worry that this might be symptom of a deeper issue on what we do with our MPI communicator, but I could not reliably reproduce the issue and identify the problem.

[charleskawczynski]

I'm curious if this is related to CliMA/ClimaCore.jl#1589. Unfortunately, I don't think we have a reproducer test in the ClimaCore test suite, but a reproducer for such an example would be very helpful.