vz: make output arguments in prlsdkGetDomainIds as optional
vz: make output arguments in prlsdkGetDomainIds as optional

prlsdkGetDomainIds() returns name and uuid for specified instance.
Now output arguments can be NULL.
It allows to get only necessary info(name or uuid).

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