test-integration-docker should use our ubuntu package mirror

CMK-33781

Change-Id: Ie5ae42f1970a6aa74eeeceb9718289105e9c4026

Author: nigelgbanks

docker_image/Dockerfile

@@ -35,6 +35,10 @@ COPY docker-entrypoint.sh /
 # Starts the entrypoint script and hands over CMD by default
 ENTRYPOINT ["/docker-entrypoint.sh"]
 
+# Use internal apt mirror
+# hadolint ignore=DL3059
+RUN sed -i "s|http://.*.ubuntu.com/ubuntu|http://apt.lan.checkmk.net/ubuntu|g" /etc/apt/sources.list.d/ubuntu.sources
+
 # Make the list of required packages available to the following command
 COPY needed-packages /needed-packages