Error out when ioslaves state that / is a regular file
Reject mounting slaves with this incompatible behaviour, it can't be mapped to FUSE semantics completely.
BUG: 433300
I'm not sure whether kio-fuse should rather try to listDir
in this case and force the root to be a directory. Subdirectories are affected the same way though, so it would be required to listDir
every file node to be sure that it's not actually a directory...