cloud filesystem: failed to format

[williamstein]

The check here is not sufficiently robust:

https://github.com/sagemathinc/cocalc-compute-docker/blob/main/src/cloud-filesystem/scripts/cloud_filesystem.py#L839

I saw an example of a cloud filesystem where we had only this:

/buckets/storage-bucket-25/juicefs$ ls 
juicefs_uuid

It thus wouldn't format it. However, it wasn't formatted. So I think we need a better test:

• that the juicefs path is there, and
• something about etcd

We should be able to check this though using juicefs.

[williamstein]

In the case where I saw this I removed /buckets/storage-bucket-25/juicefs and then it worked to format.