sheep/request: fix fd leak

This patch fixes fd leak in sheep process such as below in lsof command.

sheep 15276 liangry 95u sock 0,7 0t0 465109 can't identify protocol
sheep 15276 liangry 96u sock 0,7 0t0 464282 can't identify protocol
sheep 15276 liangry 97u sock 0,7 0t0 464284 can't identify protocol

Signed-off-by: Ruoyu <liangry@ucweb.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>