vdso: Don't miss rt-vvar while searching

As rt-vvar can be placed lower (by address) than rt-vdso,
it likely will go earlier in vma_area_list.
That means that at the moment, when we've found rt-vdso,
we already passed rt-vvar and rt_vvar_marked pointer
will not be initialized.

Search for rt-vvar during the second vma list traverse,
so we will always find it if it's present.

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>