zerotier: fix bug

1. fix config_path: create and persist
2. fix secret: support identity.secret
3. fix stop_instance: remove existing networks

net/zerotier/files/etc/init.d/zerotier

@@ -35,9 +35,10 @@ start_instance() {
 
 	# Create link or copy files from CONFIG_PATH to config_path
 	if [ -n "$config_path" -a "$config_path" != "$path" ]; then
+		# Create the config path to init and persist
 		if [ ! -d "$config_path" ]; then
-			echo "ZeroTier config_path does not exist: $config_path" 1>&2
-			return
+			echo "ZeroTier config_path does not exist: $config_path, create..."
+			mkdir -p $config_path
 		fi
 
 		# ensure that the target exists
@@ -60,7 +61,7 @@ start_instance() {
 		args="$args -p${port}"
 	fi
 
-	if [ -z "$secret" ]; then
+	if [ -z "$secret" -a ! -f $path/identity.secret ]; then
 		echo "Generate secret - please wait..."
 		local sf="/tmp/zt.$cfg.secret"
 
@@ -106,6 +107,9 @@ start_service() {
 stop_instance() {
 	local cfg="$1"
 
+	# Remove existing networks
+	rm -f ${CONFIG_PATH}_${cfg}/networks.d/*.conf
+
 	# Remove existing link or folder
 	rm -rf ${CONFIG_PATH}_${cfg}
 }