[#726] Use client time on regular requests

Use `X-Amz-Date` header as `now` when
* compute expiration epoch
* set Timestamp for object and container
* forming locks
* send notifications

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

api/layer/notifications.go

@@ -30,6 +30,7 @@ func (n *layer) PutBucketNotificationConfiguration(ctx context.Context, p *PutBu
 		Creator:      p.BktInfo.Owner,
 		Payload:      bytes.NewReader(confXML),
 		Filepath:     p.BktInfo.NotificationConfigurationObjectName(),
+		CreationTime: TimeNow(ctx),
 		CopiesNumber: p.CopiesNumber,
 	}