TT#82852 Dockerfile: update to latest grml-live version

grml-live v0.35.3 is the current release, planned to be the
base for the upcoming new Grml stable release and its release candidate.

Change-Id: Ia5916250975b90f8d5f75d6fd1aefa5a9bd17d4c

grml_build/Dockerfile

@@ -5,7 +5,7 @@ FROM docker.mgm.sipwise.com/sipwise-buster:latest
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2019-11-08
+ENV REFRESHED_AT 2020-06-04
 
 # tools for building and testing
 RUN apt-get update && apt-get install --assume-yes --no-install-recommends \
@@ -42,7 +42,7 @@ RUN echo "SECURE_BOOT=disable ./grml-live -s buster -a amd64 -c GRMLBASE,SIPWISE
 
 # base build tools
 WORKDIR /code/
-RUN git clone -b 'v0.34.3' --single-branch --depth 1 https://github.com/grml/grml-live
+RUN git clone -b 'v0.35.3' --single-branch --depth 1 https://github.com/grml/grml-live
 RUN mkdir -p /code/grml-live/templates/boot/addons/ \
   /code/grml-live/etc/grml/fai/config/files/etc/apt/sources.list.d/sipwise.list/ \
   /code/grml-live/etc/grml/fai/config/files/etc/apt/trusted.gpg.d/sipwise-keyring.gpg/ \