Bug#992187: debian-installer: Debian 11.0.0 ISO downloads packages from network (internet) even when no network mirror selected

[ValdikSS <iam@valdikss.org.ru>]

Package: debian-installer
Severity: normal
Tags: d-i

Dear Maintainer,

Debian 11.0.0 ISO file (debian-11.0.0-amd64-DVD-1.iso) silently 
downloads package index and updated .deb files from debian-security 
repository upon installation, even when no network mirror option was chosen.

I believe this is a mistake due to recent distro/updates -> 
distro-security security repository naming transaction.

HOW TO REPRODUCE:

    1. Install Debian 11.0.0 from DVD ISO file on the computer with the
       internet connection
    2. Choose "do not use internet mirror" option
    3. Check internet usage upon installation

ACTUAL RESULT:
    Wireshark shows bullseye-security repository index update and
    perl .deb packets download (perl-base, perl-modules etc).

EXPECTED RESULT:
    Internet is not used when "do not use internet mirror" option is 
chosen.

-- System Information:
Debian Release: 11.0
  APT prefers stable-security
  APT policy: (500, 'stable-security')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-8-amd64 (SMP w/2 CPU threads)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), 
LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled