We stop searching if vma->start is bigger than a required one.
The coursor is set on the last examined vma. When we are searching a
parent vma for the next vma, we start examine vma-s starting from
coursor->next, so we don't examine the vma, which is pointed by cursor.

This patch replaces list_for_each_entry_continue on list_for_each_entry_from.
Reported-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>