Hook to install json2kv to /usr/local/bin/

json2kv is needed by os-config-refresh/configure.d/52-puppet, and must be
installed on all built images.  The boot-stack element has a side effect where
it wildcard copies all files under bin/ into the built image.  However, if you
build an image with the puppet element, but not the boot-stack element, then
you do not get json2kv installed, and 52-puppet fails to run correctly.