Upon reboot VFS semi-exits all processes and unmounts the file system.
However, upon unmount, exiting FUSE file systems might need service from
the file system (due to libc). As the FUSE process is halfway the exit
procedure, it doesn't have a valid root directory and working directory.
Trying to do system calls then triggers a sanity check in VFS.
This fix first exits normal processes which should then allow for
unmounting FUSE file systems. Then VFS exits all processes including
File Servers and unmounts the rest of the file system.
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