All of ide-drive, ide-hd, ide-cd, scsi-disk, scsi-hd, and scsi-cd
supports wwn property. (NB, scsi-block doesn't support to set wwn).
* src/qemu/qemu_command.c: Error out if underlying QEMU doesn't
support wwn property for the device; Set wwn for the device otherwise.
* tests/qemuxml2argvdata/qemuxml2argv-disk-ide-wwn.args: New test
* tests/qemuxml2argvdata/qemuxml2argv-disk-ide-wwn.xml: Likewise
* tests/qemuxml2argvdata/qemuxml2argv-disk-scsi-disk-wwn.args: Likewise
* tests/qemuxml2argvdata/qemuxml2argv-disk-scsi-disk-wwn.xml: Likewise
* tests/qemuxml2argvtest.c: Add the new tests.
