ROHD-2434: Add another ARG LOFAR_BASE_IMAGE_VERSION

When a build-arg is used in athe FROM statement it kind of gets
swallowed by Docker.  In order to have access to it one has to add
another ARG statement after the FROM.

Docker/lofar-pipeline/Dockerfile.tmpl

@@ -5,6 +5,8 @@
 # Allow to specify a specific base image version.
 ARG LOFAR_BASE_IMAGE_VERSION=latest
 FROM lofar-base:${LOFAR_BASE_IMAGE_VERSION}
+# Docker mandates that this has to be done again
+ARG LOFAR_BASE_IMAGE_VERSION=latest
 ENV LOFAR_BASE_IMAGE_VERSION=${LOFAR_BASE_IMAGE_VERSION}
 
 # Add build date to the environment