Use a separate buffer for <filesystem><driver>
Use a separate buffer for <filesystem><driver>

Format the attributes in a separate buffer and only
print the element if it's not empty.

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