Description of problem:
Upgrading from Fedora 25 to Fedora 26 (older libvirt to libvirt-3.5.0-1.fc26.x86_64) broke several of my existing domains, which no longer validated according to XML.  This regression has already been fixed upstream, but needs to be backported to the Fedora build.


Version-Release number of selected component (if applicable):
libvirt-3.5.0-1.fc26.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Update a domain's <disk> description to include a line like this:

     <disk type='file' device='disk'>
      <driver type='raw' cache='none'/>
2.
3.

Actual results:
virt-xml-validate refuses to accept it, where it used to be valid. Workaround: add name='qemu' as another attribute to <driver>

Expected results:
No regression

Additional info:
Fixed upstream by commit:
commit b494e09d058f09b48d0fd8855edd557101294671
Author: Jim Fehlig <jfehlig>
Date:   Tue Jul 18 10:20:35 2017 -0600

    docs: schema: make disk driver name attribute optional
    
    /domain/devices/disk/driver/@name is not a required or mandatory
    attribute according to formatdomain, and indeed it was agreed on
    IRC that the attribute is "optional for input, recommended (but
    not required) for output". Currently the schema requires the
    attribute, causing virt-xml-validate to fail on disk config where
    the driver name is not explicitly specified. E.g.
    
    # cat test.xml | grep -A 5 cdrom
        <disk type='file' device='cdrom'>
          <driver type='raw'/>
          <target dev='hdb' bus='ide'/>
          <readonly/>
          <address type='drive' controller='0' bus='0' target='0' unit='1'/>
        </disk>
    
    # virt-xml-validate test.xml
    Relax-NG validity error : Extra element devices in interleave
    test.xml:21: element devices: Relax-NG validity error : Element domain failed to validate content
    test.xml fails to validate
    
    Relaxing the name attribute to be optional fixes the validation
    
    # virt-xml-validate test.xml
    test.xml validates