tests: qemuxml2xml: Avoid crash when processing an XML that fails to parse
tests: qemuxml2xml: Avoid crash when processing an XML that fails to parse

Failure to parse a XML that was not supposed to fail would result into a
crash in the test suite as the vcpu bitmap would not be filled prior to
the active XML->XML test.

Skip formatting of the vcpu snippet in the fake status XML formatter in
such case to avoid the crash. The test would fail anyways.

VenkatDatta/libvirt,taget/libvirt,datto/libvirt,jardasgit/libvirt,eskultety/libvirt,datto/libvirt,taget/libvirt,olafhering/libvirt,jardasgit/libvirt,crobinso/libvirt,olafhering/libvirt,andreabolognani/libvirt,nertpinx/libvirt,nertpinx/libvirt,andreabolognani/libvirt,crobinso/libvirt,jfehlig/libvirt,jardasgit/libvirt,jfehlig/libvirt,eskultety/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,crobinso/libvirt,jfehlig/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,crobinso/libvirt,eskultety/libvirt,datto/libvirt,datto/libvirt,jardasgit/libvirt,libvirt/libvirt,nertpinx/libvirt,eskultety/libvirt,zippy2/libvirt,taget/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,taget/libvirt,olafhering/libvirt,fabianfreyer/libvirt,zippy2/libvirt,eskultety/libvirt,datto/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,libvirt/libvirt,taget/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,zippy2/libvirt,olafhering/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,zippy2/libvirt