Fixed installmirrors ref

Nested inline markup is not (yet) possible: http://stackoverflow.com/a/9645684
Correct Docker run --host param to --hostname
upgrade packages after debootstrap

This makes mkimage-debootstrap upgrade packages after retrieving
updated lists of packages.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #4540 from unclejack/debootstrap_upgrade_packages

Run dist-upgrade after repo updates in mkimage-debootstrap
Merge pull request #4528 from tomfotherby/patch-1

Correct Docker run --host param to --hostname
Merge pull request #4508 from walterl/patch-1

Fixed installmirrors ref