conf: cpu: Fix parsing of vendor_id
conf: cpu: Fix parsing of vendor_id

This patch fixes a problem that vendor_id attribute can not be defined
when fallback attribute is not defined.

If I define domain xml like below:
<domain>
  <cpu>
    <model vendor_id='aaaabbbbcccc'>core2duo</model>
  </cpu>
</domain>

In dumpxml, vendor_id is not reflected:
<domain>
  <cpu mode='custom' match='exact'>
    <model fallback='allow'>core2duo</model>
  </cpu>
</domain>

The expected output is:
<domain>
  <cpu mode='custom' match='exact'>
    <model fallback='allow' vendor_id='aaaabbbbcccc'>core2duo</model>
  </cpu>
</domain>

If the fallback attribute and vendor_id attribute is defined at the same
time, it's reflected as expected.

Signed-off-by: Ken ICHIKAWA <1052601581d4baeed95ab542ce6f4548d275cb36@jp.fujitsu.com>

jardasgit/libvirt,olafhering/libvirt,bjzhang/libvirt,trainstack/libvirt,fabianfreyer/libvirt,zippy2/libvirt,emaste/libvirt,crobinso/libvirt,zippy2/libvirt,iam-TJ/libvirt,libvirt/libvirt,emaste/libvirt,zippy2/libvirt,cbosdo/libvirt,jfehlig/libvirt,libvirt/libvirt,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,olafhering/libvirt,datto/libvirt,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,trainstack/libvirt,VenkatDatta/libvirt,zhlcindy/libvirt-1.1.4-maintain,crobinso/libvirt,shugaoye/libvirt,olafhering/libvirt,jardasgit/libvirt,nertpinx/libvirt,eskultety/libvirt,cbosdo/libvirt,agx/libvirt,iam-TJ/libvirt,crobinso/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,trainstack/libvirt,siboulet/libvirt-openvz,trainstack/libvirt,iam-TJ/libvirt,bjzhang/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,jardasgit/libvirt,trainstack/libvirt,emaste/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,datto/libvirt,bjzhang/libvirt,rlaager/libvirt,VenkatDatta/libvirt,siboulet/libvirt-openvz,fabianfreyer/libvirt,jardasgit/libvirt,andreabolognani/libvirt,emaste/libvirt,emaste/libvirt,elmarco/libvirt,zippy2/libvirt,cbosdo/libvirt,eskultety/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,cbosdo/libvirt,elmarco/libvirt,nertpinx/libvirt,libvirt/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,rlaager/libvirt,andreabolognani/libvirt,iam-TJ/libvirt,jfehlig/libvirt,emaste/libvirt,nertpinx/libvirt,rlaager/libvirt,bjzhang/libvirt,cbosdo/libvirt,crobinso/libvirt,agx/libvirt,andreabolognani/libvirt,taget/libvirt,agx/libvirt,rlaager/libvirt,siboulet/libvirt-openvz,andreabolognani/libvirt,datto/libvirt,olafhering/libvirt,trainstack/libvirt,taget/libvirt,libvirt/libvirt,andreabolognani/libvirt,agx/libvirt,fabianfreyer/libvirt,taget/libvirt,taget/libvirt,eskultety/libvirt,elmarco/libvirt,iam-TJ/libvirt,shugaoye/libvirt,iam-TJ/libvirt,datto/libvirt,taget/libvirt,nertpinx/libvirt,emaste/libvirt,VenkatDatta/libvirt,trainstack/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,elmarco/libvirt,jfehlig/libvirt,datto/libvirt,bjzhang/libvirt,siboulet/libvirt-openvz,eskultety/libvirt,elmarco/libvirt,nertpinx/libvirt,eskultety/libvirt