domaincapstest: Run cleanly on systems missing OVMF firmware
domaincapstest: Run cleanly on systems missing OVMF firmware

As of f05b6a918e28 the test produces the list of paths that can
be passed to <loader/> and libvirt knows about them. However,
during the process of generating the list the paths are checked
for their presence. This may produce different results on
different systems.  Therefore, the path - if missing - is
added to pretend it's there.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

olafhering/libvirt,eskultety/libvirt,taget/libvirt,zippy2/libvirt,shugaoye/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,libvirt/libvirt,jfehlig/libvirt,datto/libvirt,datto/libvirt,eskultety/libvirt,andreabolognani/libvirt,taget/libvirt,zippy2/libvirt,datto/libvirt,crobinso/libvirt,fabianfreyer/libvirt,rlaager/libvirt,jfehlig/libvirt,eskultety/libvirt,eskultety/libvirt,olafhering/libvirt,jfehlig/libvirt,agx/libvirt,rlaager/libvirt,olafhering/libvirt,rlaager/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,taget/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,agx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,datto/libvirt,agx/libvirt,elmarco/libvirt,agx/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,crobinso/libvirt,datto/libvirt,jardasgit/libvirt,nertpinx/libvirt,elmarco/libvirt,rlaager/libvirt,nertpinx/libvirt,taget/libvirt,jardasgit/libvirt,elmarco/libvirt,zippy2/libvirt,crobinso/libvirt,rlaager/libvirt,elmarco/libvirt,olafhering/libvirt,eskultety/libvirt,jardasgit/libvirt,taget/libvirt,VenkatDatta/libvirt,agx/libvirt,crobinso/libvirt,andreabolognani/libvirt,elmarco/libvirt,nertpinx/libvirt,jfehlig/libvirt,shugaoye/libvirt,libvirt/libvirt,andreabolognani/libvirt,libvirt/libvirt,shugaoye/libvirt,nertpinx/libvirt