The guest firmware provides the same functionality as the pvpanic
device, and the relevant element should always be present in the
domain XML to reflect this fact, so add it after parsing the
definition if it wasn't there already.
There are no options to parse here other than the name of the device,
and all three possible device names have the same prefix
("virtio-balloon" with "-ccw", "-pci", or "-device" appended), so the
code is fairly simple. It has been implemented such that it will be
easier to add handling for other -device entries that aren't otherwise
recognized - just add another "else if (STRPREFIX(opts, ....)" clause.
qemuParseCommandLineString() previously would always add a <memballoon
model='virtio'/> to every result (the comments erroneously say that it
is adding a <memballoon model='none'/>) This has been changed to add
model='none', and 84 test case xml's updated accordingly (so that
qemuxml2argvtest won't fail).
Now that the memballoon device is properly parsed, we can safely add a
test for properly ignoring -nodefconfig and -nodefaults. Rather than
adding an entire new test case for this (and memballoon), we just
randomly pick the clock-utc test and modify it slightly to fulfill the
purpose.
<controller type='pci' index='0' model='pci-root'/>
is auto-added to pc* machine types.
Without this controller PCI bus 0 is not available and
no PCI addresses are assigned by default.
Since older libvirt supported PCI bus 0 even without
this controller, it is removed from the XML when migrating.
