Bug#860079: apt-setup: allow_unauthenticated not honoured, disables added repository for lack of key

[Kegan Holtzhausen <marzubus@gmail.com>]

Package: apt-setup
Severity: minor
Tags: d-i

Dear Maintainer,

*** Reporter, please consider answering these questions, where appropriate ***

   * What led up to the situation?
	preseed specifying a local0 apt server, and setting allow-unauthenticated to true, 
	still results in the new server being disabled in the sources.list
   * What exactly did you do (or not do) that was effective (or
     ineffective)?
	setting d-i debian-installer/allow_unauthenticated boolean true in preseed
	yields no change, it seems key needs to be set for repo.
   * What was the outcome of this action?
	my new repository was commented out in sources.list as being unauthenticated / insecure
   * What outcome did you expect instead?
	Expected my local repository to be enabled in sources.list

*** End of the template - remove these template lines ***


-- System Information:
Debian Release: 8.7
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.13-moby (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/dash
Init: unable to detect