docker: Disable avahi by default. Suspected to be buggy.

docker/fs/etc/s6-overlay/s6-rc.d/avahi/run

@@ -1,5 +1,12 @@
 #!/bin/bash
 
+if [ -z "$SCRYPTED_DOCKER_AVAHI" ]
+then
+  while true
+    sleep 1000
+  done
+fi
+
 until [ -e /var/run/dbus/system_bus_socket ]; do
   echo "Waiting for dbus..."
   sleep 1s