Follow Salsa-CI changes and update build image name to 'dockerbuilder'

This is needed to get the Gitlab pipeline passing again. Without this
it will fail with error message:
  /usr/bin/chown: invalid user: 'salsa-ci:0'

debian/.gitlab-ci.yml

@@ -23,7 +23,7 @@ build package:
   script:
     - gbp pull --ignore-branch --pristine-tar --track-missing
     - while true; do sleep 600; echo "10 minutes passed" >&2; done & # Progress keeper since build is long and silent
-    - gbp buildpackage --git-ignore-branch --git-export-dir=${WORKING_DIR} -us -uc --git-builder="docker-build.sh registry.salsa.debian.org/salsa-ci-team/images/base:${RELEASE}" | tail -n 10000 # Keep log under 4 MB
+    - gbp buildpackage --git-ignore-branch --git-export-dir=${WORKING_DIR} -us -uc --git-builder="docker-build.sh registry.salsa.debian.org/salsa-ci-team/images/dockerbuilder:${RELEASE}" | tail -n 10000 # Keep log under 4 MB
     - du -shc ${WORKING_DIR}/* # Show total file size of artifacts. Must stay are under 100 MB.
 
 # Autopkgtest must be disabled, because the test 'upstream' will be skipped and