So since the introduction of the memory-backend-file object until now we
only added '-mem-path' for non-NUMA guests and we used the parameters of
the memory-backend-file object to specify the path to the hugetlbfs
mount.  But hugepages can be also used without memory-backend-file
object, as it used to be before its introduction.  Let's just get this
part of the code back and properly append the '-mem-path' for NUMA
guests as well, but only when the memory backend is not needed.

This parameter is already being applied when no numa is requested and
because we still use memory-object-file unconditionally for
hugepage-backed NUMA guests, this should not fire until later.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>