CLOUDRON_APP_HOSTNAME should be the app id always

name is the container name which is "unique"

src/docker.js

@@ -187,7 +187,7 @@ function createSubcontainer(app, name, cmd, options, callback) {
     let stdEnv = [
         'CLOUDRON=1',
         'CLOUDRON_PROXY_IP=172.18.0.1',
-        `CLOUDRON_APP_HOSTNAME=${name}`,
+        `CLOUDRON_APP_HOSTNAME=${app.id}`,
         `${envPrefix}WEBADMIN_ORIGIN=${config.adminOrigin()}`,
         `${envPrefix}API_ORIGIN=${config.adminOrigin()}`,
         `${envPrefix}APP_ORIGIN=https://${domain}`,