nspawn: explicitly terminate machines when we exit nspawn

https://bugs.freedesktop.org/show_bug.cgi?id=68370
https://bugzilla.redhat.com/show_bug.cgi?id=988883

Conflicts:
	src/nspawn/nspawn.c

Conflicts:
	src/nspawn/nspawn.c
bash-completion: journalctl --file

Conflicts:
	shell-completion/bash/journalctl
journalctl,zsh-completion: fix several issues in --help message text

-- fix grammar and reword some descriptions for clarity
-- add a useful description of what --follow does
-- fix the description for --after-cursor
-- properly introduce the FSS acronym for "Forward Secure Sealing" in
both sections
-- clarify the --disk-usage command

[zj: perform similar changes to zsh completions]

squash! journalctl: fix several issues in --help message text

Conflicts:
	src/journal/journalctl.c

Conflicts:
	shell-completion/zsh/_journalctl
	src/journal/journalctl.c
fstab-generator: Do not try to fsck non-devices

This fixes a regression introduced in 64e70e4 where the mount fails
when fstab is misconfigured with fs_passno > 0 on a virtual file
system like nfs, and the type is specified as "auto".

Conflicts:
	src/fstab-generator/fstab-generator.c