[BENTO-36] Fix remaining manual prompts in auto-install. Suppress Deb…

…ian's own Virtualbox extensions from being installed in the bento box. Switch to mirrors.kernel.org; the main Debian site doesn't seem to be the most reliable and causes builds to fail.

definitions/.debian/preseed.cfg

@@ -1,4 +1,3 @@
-choose-mirror-bin mirror/http/proxy string
 d-i base-installer/kernel/override-image string linux-server
 d-i clock-setup/utc boolean true
 d-i clock-setup/utc-auto boolean true
@@ -7,7 +6,7 @@ d-i grub-installer/only_debian boolean true
 d-i grub-installer/with_other_os boolean true
 d-i mirror/country string manual
 d-i mirror/http/directory string /debian
-d-i mirror/http/hostname string http.us.debian.org
+d-i mirror/http/hostname string mirrors.kernel.org
 d-i mirror/http/proxy string
 d-i partman-auto-lvm/guided_size string max
 d-i partman-auto/choose_recipe select atomic
@@ -32,8 +31,14 @@ d-i pkgsel/include string openssh-server sudo bzip2 acpid cryptsetup zlib1g-dev
 d-i pkgsel/install-language-support boolean false
 d-i pkgsel/update-policy select unattended-upgrades
 d-i pkgsel/upgrade select full-upgrade
+# Prevent packaged version of VirtualBox Guest Additions being installed:
+d-i preseed/early_command string sed -i \
+  '/in-target/idiscover(){/sbin/discover|grep -v VirtualBox;}' \
+  /usr/lib/pre-pkgsel.d/20install-hwpackages
 d-i time/zone string UTC
 d-i user-setup/allow-password-weak boolean true
 d-i user-setup/encrypt-home boolean false
+apt-cdrom-setup apt-setup/cdrom/set-first boolean false
+apt-mirror-setup apt-setup/use_mirror boolean true
 popularity-contest popularity-contest/participate boolean false
 tasksel tasksel/first multiselect standard, ubuntu-server