Correct zerotier role to be more clear about apt-centricity

roles/zerotier/tasks/main.yml

@@ -1,6 +1,8 @@
 #!/usr/bin/env ansible-playbook
 # vim:ft=ansible:
 ---
+- name: configure zerotier for apt
+  block:
     - name: ensure zerotier repo key
       apt_key: url=https://raw.githubusercontent.com/zerotier/ZeroTierOne/master/doc/contact%40zerotier.com.gpg
     - name: ensure zerotier repo
@@ -9,6 +11,7 @@
       apt: update_cache=yes cache_valid_time=86400
     - name: ensure packages
       apt: name=zerotier-one
+  when: ansible_pkg_mgr == "apt"
 - name: template unit file
   template: src=zerotier-one.service dest=/etc/systemd/system/zerotier-one.service
   notify: restart zerotier