Revert "Add tests into tst-fs-link.so to check vnode duplicity"

This reverts commit bdd99c7b2d3a6852c5422852449d1e5c7e9a77d3.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Revert "vfs: Fix duplicate in-memory vnodes"

This reverts commit e4aad1baabc326d11eebb05622832563d616cb60.

It causes tst-vfs.so to just hang.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>