Bug#901332: d-i: Offer to shut down / power off instead of reboot at the end

[Thorsten Glaser <tg@mirbsd.de>]

Package: debian-installer
Severity: normal

d-i always insists on rebooting at the end. This is made worse
by it telling the user to change boot media, which, for virtual
machines, means reconfiguring the VM.

I *generally* wish to reconfigure the VM after first install
*anyway*.

So, please, at the end, where it tells the reboot message, add
a third button that shuts down / powers off the system instead
of rebooting.

Thanks in advance!

-- System Information:
Debian Release: buster/sid
  APT prefers unreleased
  APT policy: (500, 'unreleased'), (500, 'buildd-unstable'), (500, 'unstable'), (100, 'experimental')
Architecture: x32 (x86_64)
Foreign Architectures: i386, amd64

Kernel: Linux 4.15.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=C, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=C (charmap=UTF-8)
Shell: /bin/sh linked to /bin/lksh
Init: sysvinit (via /sbin/init)