A way to switch cdroms live

[yamamushi]

If I provide the path to the first iso, and the second iso, we should be able to take commands to choose which cdrom to boot.

This is necessary for RedStar Linux Server (North Korea Linux), as part of the installation requires switching the cdroms.

http://blog.siphos.be/2010/08/qemu-monitor-cd-change/

http://blog.famzah.net/2010/01/09/changing-the-iso-image-in-a-virtual-cdrom-drive-while-kvm-qemu-is-running/