fsnotofy: Do remap resolve in post-prep

The remap is searhced by dev:ino pair that is known only when
root task starts (and opend the remap). The collection stage
is about to happen in crtools, so move the resolve in post-prep.

Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>