docker: eliminate copy-json.py in favor of json-file

docker: eliminate copy-json.py in favor of json-file

This patch rewires how we configure the Kolla external config files
via Heat templates and uses a more simple json-file heat hook to
directly write out Kolla config files to disk.

By using a heat hook instead of a shell script we can avoid
Json conversion issues.  Additionally, This generic json file hook will
be useful for other ad-hoc Json file configuration within the TripleO
docker architecture.

Co-Authored-By: Martin André <m.andre@redhat.com>
Change-Id: I8c72a4a9a7022f722bfe1cef3e18517605720cce
Depends-On: I2b372ac2e291339e436202c9fe58a681ed6a743f
Depends-On: Id3f779b11e23fd3122ef29b7ccbae116667d4520