FUSE: avoid logging normal conditions like ENOENT

$ swh fs mount -f ~/swh-environment/swhfs
[...]
ERROR:root:Cannot lookup: unknown name: .Trash
Traceback (most recent call last):
  File "/home/zack/dati/projects/sw-heritage/git/swh-environment/swh-fuse/swh/fuse/fuse.py", line 226, in lookup
    raise ValueError(f"unknown name: {name}")
ValueError: unknown name: .Trash
ERROR:root:Cannot lookup: unknown name: .Trash-1000
[...]
ValueError: unknown name: .Trash-1000
[...]
ValueError: unknown name: BDMV
[...]
ValueError: unknown name: .xdg-volume-info

The above are not errors, just normal conditions of a filesystem, we should not log them as errors (and certainly not log their tracebacks).

The above is specific to ENOENT, there might be other similar conditions to avoid logging to.

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Migrated from T2802 (view on Phabricator)