Fix: use most recent meta data representation
Fix: use most recent meta data representation

This commit changes slightly the JSON format used for describing data
sources. The library now writes the most recently defined version.

Unfortunately the RRD protocol is not explicitly versioned and only
testing brought the problem to light.

Signed-off-by: Christian Lindig <4f88b50bc9dba63c9a7d9e208d4b3ac6f1a52800@citrix.com>

xapi-project/rrd-client-lib,lindig/rrd-client-lib-1