The `$(</path/to/file)`-expansion appears verbatim in the cmdline of
`nextcloud-occ` which means that an unprivileged user could find
sensitive values (i.e. admin password & database password) by monitoring
`/proc/<pid>/cmdline`.
Now, these values don't appear in a command line anymore, but will be
passed as environment variables to `nextcloud-occ`.
(cherry picked from commit 9f37d6aee028679b8a94be59d74984e708acaa85)
e33cbdc2de