Set up Zerotier Control UI

Install/configure ztncui[1], with HTTP access allowed from within the
private network.

[1]: https://key-networks.com/ztncui/

site-cookbooks/kosmos_zerotier/attributes/default.rb

@@ -1 +1,6 @@
-node.default["kosmos_zerotier"]["server_port"] = 9993
+node.default['kosmos_zerotier']['server_port'] = 9993
+
+node.default['ztncui']['version'] = '0.6.6'
+node.default['ztncui']['checksum'] = 'fa83679266a571c10e13b11293ebfb9d1c3515019f2af1e7dd066b5a37411018'
+node.default['ztncui']['http_all_interfaces'] = true
+node.default['ztncui']['http_allow_access_from'] = '10.1.1.0/24'