Remove apt-get dist-upgrade from Dockerfile

The Docker best practices at https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#apt-get recommends you don't run apt-get dist-upgrade in your container, but instead use a current upstream image. Follow this recommendation.

Author: robinsmidsrod

Dockerfile

@@ -6,7 +6,6 @@ ARG DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get -q -y update \
  && apt-get -q -y -o "DPkg::Options::=--force-confold" -o "DPkg::Options::=--force-confdef" install apt-utils \
- && apt-get -q -y -o "DPkg::Options::=--force-confold" -o "DPkg::Options::=--force-confdef" dist-upgrade \
  && apt-get -q -y -o "DPkg::Options::=--force-confold" -o "DPkg::Options::=--force-confdef" install dumb-init isc-dhcp-server man \
  && apt-get -q -y autoremove \
  && apt-get -q -y clean \