Build multiple airflow images with specific uid/values for task runners
We plan to use specific images for each of the airflow task runners, in order to simplify the kerberos authentication and the interaction with HDFS file permissions.
This commit renames the 'production' variant to be 'base' and we exchange 'runuser' for 'airflow' in this image.
Then six other images are built, each of which has a specific user for the .runs.as parameter, which matches the users we need for kerberos and HDFS.
Bug: T375895