use cdrom in docker container.

1. make sure you never mount your cdrom.
2. run you container using the command like ``` docker run -i -t -v /dev/cdrom:/dev/cdrom dockerfiles/centos-lamp /bin/bash```
3. type ```mkdir /mnt/cdrom``` in your container bash.
4. type ```mount -t iso9660 -o ro /dev/cdrom /mnt/cdrom``` in your container bash.
5. see you cdrom using ```ls /mnt/cdrom``` in your container bash.