add metadata.json file
add metadata.json file

This file will be useful to contain the release tag so we can
automatically generate tarballs in OpenStack Infra.
No requirements have been set, on purpose, because we won't use
puppetlabs forge to install the module.

Change-Id: Iada2ba5ff37760537cd15630333d2e80550fc031

paramite/puppet-tripleo,paramite/puppet-tripleo,paramite/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo