Bug#1079087: xen-create-image does not use /etc/apt/sources.list mirror

On an adjacent matter, there's a minor issue that https://sources.debian.org/src/xen-tools/4.9.2-1/hooks/common/20-setup-apt#L38 reports use of a proxy even when there is none.

Bug#1079087: xen-create-image does not use /etc/apt/sources.list mirror

Package: xen-tools Version: 4.9.2-1 Severity: normal X-Debbugs-Cc: deb...@good-with-numbers.com According to xen-create-image(8): --mirror=url Setup the mirror to use when installing via debootstrap. (Default value: mirror used in /etc/apt/sources.list or for Debia