Using getattr when follow-symlink is enabled causes invalid type to the kernel if symlink pointed to non-symlink.
* follow-symlinks: allows mergerfs to transparently follow symlinks * link-exdev: in the event a link returns EXDEV create a symlink instead * rename-exdev: in the event a rename returns EXDEV move the oldpath and create a symlink for the newpath
Also added unit tests. Should have done separately but found a number of bugs.