xfrm: clone XFRMA_REPLAY_ESN_VAL in xfrm_do_migrate

XFRMA_REPLAY_ESN_VAL was not cloned completely from the old to the new.
Migrate this attribute during XFRMA_MSG_MIGRATE

v1->v2:
 - move curleft cloning to a separate patch

Fixes: af2f464e ("xfrm: Assign esn pointers when cloning a state")
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>