create an isolated docker network named cloudron

we will move from linked containers to an isolated network. This
has the main advantage that linked containers can be upgraded.
For example, I can update the mysql container independently without
breaking the apps that require it. Apps will only see some minor
downtime and will need to reconnect.

src/platform.js

@@ -44,6 +44,7 @@ function initialize(callback) {
 
     async.series([
         stopContainers,
+        createDockerNetwork,
         startAddons,
         removeOldImages,
         existingInfra.version === 'none' ? apps.restoreInstalledApps : apps.configureInstalledApps,
@@ -73,6 +74,10 @@ function stopContainers(callback) {
     callback();
 }
 
+function createDockerNetwork(callback) {
+    shell.execSync('createDockerNetwork', 'docker network create --subnet=172.18.0.0/16 cloudron || true', callback);
+}
+
 function startGraphite(callback) {
     const tag = infra.images.graphite.tag;
     const dataDir = paths.DATA_DIR;