fs: Directory: Reduce locked scope
fs: Directory: Reduce locked scope

This should fix the report of a lock inversion. The event was registered
without the internal vlc lock, and the event handler was locking the
medialibrary lock, but the event was unregistered with the medialibrary
lock held before locking the internal vlc lock

chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary