Make `gocryptfs.diriv` and `gocryptfs.xxx.name` files world-readable to make encrypted backups easier
when mounting via fstab.
Having the files follow chmod/chown of their parent does not seem
to be worth the hassle. The content of the diriv files is not
secret, and both diriv and name files are protected by the
perms of the parent dir.
When a process has its working dir inside the mount,
the only way we notice is that we get EBUSY when trying
We used to lazy-unmount in this case, but this means
pulling the rug from under the process.
For example, bash will start throwing
cd: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory