For emulated CDROM media, set the params to the qemu blkfront's device, rather than the storage domain device.
For emulated CDROM media, set the params to the qemu blkfront's device, rather than the storage domain device.

This is needed because qemu can only read paths within its own domain.

In the case of the storage domain = the qemu domain, the qemu blkfront's device should be the same as the storage domain device.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

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