Adds am_lighthouse warning msg (#43)

* add warning message when am_lighthouse is enabled; update config templating

examples/quickstart-vagrant/ansible/roles/nebula/templates/config.yml.j2

@@ -42,8 +42,10 @@ lighthouse:
   am_lighthouse: false
 {% endif %}
   interval: 60
+{% if 'generic' in group_names %}
   hosts:
     - {{ hostvars[groups['lighthouse'][0]][vagrant_ifce]['ipv4']['address'] | to_nebula_ip }}
+{% endif %}
   
 # Configure the private interface
 tun:

main.go

@@ -188,6 +188,13 @@ func Main(configPath string, configTest bool, buildVersion string) {
 
 	punchBack := config.GetBool("punch_back", false)
 	amLighthouse := config.GetBool("lighthouse.am_lighthouse", false)
+
+	// warn if am_lighthouse is enabled but upstream lighthouses exists
+	lighthouseHosts := config.GetStringSlice("lighthouse.hosts", []string{})
+	if amLighthouse && len(lighthouseHosts) != 0 {
+		l.Warn("lighthouse.am_lighthouse enabled on node but upstream lighthouses exist in config")
+	}
+
 	serveDns := config.GetBool("lighthouse.serve_dns", false)
 	lightHouse := NewLightHouse(
 		amLighthouse,