Improve zerotier checks

roles/zerotier/tasks/main.yml

@@ -1,9 +1,13 @@
 #!/usr/bin/env ansible-playbook
 # vim:ft=ansible:
 ---
-- name: check for zerotier
+- name: check for zerotier in /usr/bin
   stat: path=/usr/bin/zerotier-cli
   register: zerotier_cli_path
+- name: check for zerotier in /usr/sbin
+  stat: path=/usr/sbin/zerotier-cli
+  register: zerotier_cli_path
+  when: not zerotier_cli_path.stat.exists
 - name: install zerotier if we're joining networks
   block:
     - name: configure zerotier for apt