https://bugzilla.redhat.com/show_bug.cgi?id=1135396

There are two ways how to tell qemu to use huge pages. The first one
is suitable for domains with NUMA nodes: the path to hugetlbfs mount
is appended to NUMA node definition on the command line. The second
one is suitable for UMA domains: here there's this global '-mem-path'
argument that accepts path to the hugetlbfs mount point. However, the
latter case was not used for all the cases that it should be. For
instance:

  <memoryBacking>
    <hugepages>
      <page size='2048' unit='KiB' nodeset='0'/>
    </hugepages>
  </memoryBacking>

didn't trigger the '-mem-path' so the huge pages - despite being
configured - were not used at all.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>