execute: more debugging messages
gpt-auto-generator: exit immediately if in container

Otherwise we get an ugly warning when running systemd in
a container.
Introduce _cleanup_endmntent_
systemd: order remote mounts from mountinfo before remote-fs.target

Usually the network is stopped before filesystems are umounted.
Ordering network filesystems before remote-fs.target means that their
unmounting will be performed earlier, and can terminate sucessfully.

https://bugs.freedesktop.org/show_bug.cgi?id=70002