NiFi Registry Docker Image builds are inconsistent (dockermaven vs. dockerhub)

The dockermaven and dockerhub image builds are not consistent, e.g. then have different startup scripts copied into the images (some of which contain issues like incorrect properties being used).

See https://github.com/apache/nifi/pull/6995 (for NIFI-7060) for a more complete list of known inconsistences that should be fixed.