Update package manager cache before install

As it currently stands, after the repo is added, apt-get update (or equivalent) is not performed, and zerotier-one install fails.

tasks/install.yml

@@ -10,6 +10,7 @@
     package:
       name: zerotier-one
       state: present
+      update_cache: yes
     register: zerotier_client
 
   - name: Start zerotier-one service