Add supervisord-dependent-startup, restructure file layout

root/etc/supervisor.d/docker.conf

@@ -0,0 +1,8 @@
+[program:dockerd]
+command=/usr/local/bin/dockerd-entrypoint.sh
+stdout_logfile_maxbytes=0
+stdout_logfile=/dev/fd/1
+redirect_stderr=true
+startsecs=20
+dependent_startup=true
+autostart=false