The helper function aims to reset cpu related vars to none except
<topology>.
It is named with clear_attrs(). clear() could be saved for later use
of clearing all of them including <topology>.
With this patch, users can use cpu host-passthrough like this:
virt-install --cpu host-passthrough ...
Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
(crobinso: Add Hu Tao to AUTHORS)
