autotest/virt-test — pull request #480 by QiuMike (2013-05-28 09:15:39+00:00)
Title: virttest.qemu_vm: use add_cdrom if cd_format is none

In the situation of cd_format is none, it will use 'ide'
for cdrom, it may be correct in x86, but ppc64 QEMU doesn't
support 'ide'.

So use add_cdrom(), if cd_format is none, to make both arch works.

Signed-off-by: Mike Qiu