Re: [Libguestfs] [PATCH] drives: add CD-ROM disk images as read-only drives (RHBZ#563450).

The current add_cdrom way basically appends a new raw "-cdrom /path" parameter to the qemu invocation (even when using libvirt as backend), hence such images are seen as "CD-ROM drives" inside the appliance. However, there is no need for such particular behaviour, as they need to be handled as normal (read-only) drives. Adding CD-ROM disk images as drives also changes the device names used for them inside the appliance from /dev/srN to the usual e.g. /dev/sdX. These changes fix different issues: - it is possible to start guestfish without adding disks with -a, then just add-cdrom and run - list-devices does not cause guestfsd to crash when sorting the list of devices (exposed by the test case in RHBZ#563450) - the result of list-devices now reflects the order images were added (RHBZ#563450) add_cdrom is still deprecated, but now in favour of add_drive_ro (instead of add_drive), with its documentation reflecting that. Add two small regression tests for the fixes described above.