Change to code to unmount cdrom due to change in proxmox format

[Quiphius]

Proxmox has changed the config format of the cdrom and HasSuffix won't work anymore, changed to Contains to allow the string "media=cdrom" to be anywhere in the response.

Closes #83

[walmins]

Hello people,
do you schedule the merge date for this bug because we are blocked also?

Thanks

[vrubiolo]

Hi there,

We are interested by the fix too as we hit this issue this week and are also blocked. Let us know if you need assistance testing things.

[nywilken]

Apologies for the delayed review here. This looks good to me. Thank you for the fix.
It will go out with the next release, which will happen fairly soon.