Create /etc/ansible/facts.d/zerotier.fact on each node containing custom facts in json format. This can then be used to prevent pointless reconfiguration of existing nodes whenever a new one is added to the inventory. In this commit it merely skips the installation tasks.
Give the user an option to skip the installation tasks. There's no real need to download the pgp key and packages again when all you want to do is reconfigure existing members.
Marcus Meurs
Andy Shinn