fix build on eoan

docker/Dockerfile

@@ -1,13 +1,9 @@
-# docker build --pull --force-rm --rm -t dev0004:5000/library/webtester .
-# docker push dev0004:5000/libray/webtester
-FROM ubuntu:latest
+FROM mwaeckerlin/ubutu-base
 MAINTAINER "Marc Wäckerlin"
 
-RUN apt-get install -y wget software-properties-common apt-transport-https
-RUN apt-add-repository https://dev.marc.waeckerlin.org/repository
-RUN wget -O- https://dev.marc.waeckerlin.org/repository/PublicKey | apt-key add -
-RUN apt-get update -y
-RUN apt-get install -y xvfb webtester
+RUN apt-get update \
+ && apt-get install --no-install-recommends --no-install-suggests -y xvfb webtester \
+ && /cleanup.sh
 
 ADD runtests.sh runtests.sh