Unlike the FUSE implementation on Linux, macFUSE doesn't cache the file
attributes from the `LOOKUP` call, so it calls `GETATTR` prior to
accessing a file.
In the case of the `VirtualConfNode` (reverse config file passthrough),
this resulted in the default `GETATTR` implementation returning an empty
result, ultimately resulting in a "permission denied" error.
14:44:14.095207 rx 3: GETATTR n2
14:44:14.095229 tx 3: OK, {tA=1s {M0100000 SZ=0 L=0 0:0 0 0:8954996 A 0.000000 M 0.000000 C 0.000000}}
14:44:14.099943 rx 4: ACCESS n2 {u=501 g=20 r}
14:44:14.099990 tx 4: 13=permission denied
By impementing `Getattr` (from `fs.NodeGetattrer`) on `VirtualConfNode`
this solves the issue.
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