By default a list item in a JSON or YAML format will extend if a its already
defined in the target template and a config_override using a list is being set
for the existing "key".
This change allows that functionality to be toggled on or off. The boolean
option to enable list extension is ``list_extend``.
To maintain the API this feature will remain True by default.
Co-Authored-By: Travis Truman <travis_truman@cable.comcast.com>
Change-Id: I97e06aef2cc778f048f3d6863fe61d10eddb8602
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>
