sserver: Fix cannot send notify when no new job; Keep at least one job even if it expired
sserver: Fix cannot send notify when no new job; Keep at least one job even if it expired

btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool