test_restart fails when using `cloud_model: grid_scale` and `turbconv: nothing`

We don't test this combination in our list of configs for restart test here: https://github.com/CliMA/ClimaAtmos.jl/blob/b595daf1075282d1b888ac7759755ac3f3d52855/test/restart.jl#L341. But this will fail because some cache is allocated (e.g. ᶜlinear_buoygrad) but never computed or used, so they are assigned to some random values. But the restart test compares everything in the cache.