The `merge` option will basically copy all the files recursively inside
the container without removing the existing files or directory, while
the `preserve_properties` option keeps the file attributes
(permissions, ownership, timestamps) in the container.
This is useful if you have extracted some config files from a container
and want to use them in another container based on the same image.
This makes TripleO usage of Kolla much more robust.
Change-Id: I78dcec741a941dc21adba33ba33a6dc6ff1d217c