Mutex locking order

Right now, we have several parallel Mutexes in use in fs_interface:
Arbo, LocalConfig, GlobalConfig

If the order of locking these is not the same, then a deadlock could occur

The only way I know of enforcing it, is to lock them behind each other.

A LocalConfig lock requires a GlobalConfig lock requires a Arbo lock

This means that GlobalConfig' RwLock would be owned by Arbo, and LocalConfig's RwLock would be owned by GlobalConfig