ARTEMIS-4408 Update docker-run.sh for etc override
After creating the artemis docker image using the docker-run.sh script,
it is not possible to map a user supplied broker.xml using a volume
mapping. The broker.xml file is not there before instance creation,
so we cannot a static file mapping.
This change introduces an etc-override folder to write over the etc
folder contents. If a folder named etc-override exists inside the
instance folder, its contents will be copied over to etc folder after
instance creation. In order to use custom files that reside in etc,
eg. broker.xml or artemis.profile; it is sufficient to place these
files to a folder and map it to /var/lib/artemis-instance/etc-override
folder of the image.
The usage is also documented in readme.md file under the docker folder.
Fixes the Dockerfiles handling of ANONYMOUS_LOGIN and adds an
EXTRA_ARGS environment variable to allow specifying extra arguments
separate from the username, password and anonymous login options.