Main test features:
- Non trivial ps tree with non trivial anon shmem regions
  (no such test exists now).
- Each ps tree process continuously writes parts of anon shmem
  vmas and validates these writes after restore
  (required for dedup testing).
- Checking simultaneous changing of anon shmem contents in different
  processes.
Signed-off-by: Eugene Batalov <eabatalov89@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>