HAWQ-1338. Fixed writer process doesn't exit nicely in some case
HAWQ-1338. Fixed writer process doesn't exit nicely in some case

Signed-off-by: Ivan Weng <f666cc6600203c0dd097225be80bd8825d72325e@apache.org>

wengyanqing/incubator-hawq,wengyanqing/incubator-hawq,huor/incubator-hawq,outofmem0ry/incubator-hawq,jianlirong/incubator-hawq,jianlirong/incubator-hawq,wengyanqing/incubator-hawq,wengyanqing/incubator-hawq,huor/incubator-hawq,stanlyxiang/incubator-hawq,stanlyxiang/incubator-hawq,outofmem0ry/incubator-hawq,jianlirong/incubator-hawq,lavjain/incubator-hawq,wengyanqing/incubator-hawq,wengyanqing/incubator-hawq,huor/incubator-hawq,outofmem0ry/incubator-hawq,outofmem0ry/incubator-hawq,jianlirong/incubator-hawq,huor/incubator-hawq,wengyanqing/incubator-hawq,stanlyxiang/incubator-hawq,jianlirong/incubator-hawq,lavjain/incubator-hawq,stanlyxiang/incubator-hawq,lavjain/incubator-hawq,outofmem0ry/incubator-hawq,huor/incubator-hawq,lavjain/incubator-hawq,stanlyxiang/incubator-hawq,huor/incubator-hawq,lavjain/incubator-hawq,lavjain/incubator-hawq,outofmem0ry/incubator-hawq,huor/incubator-hawq,outofmem0ry/incubator-hawq,jianlirong/incubator-hawq,jianlirong/incubator-hawq,jianlirong/incubator-hawq,stanlyxiang/incubator-hawq,lavjain/incubator-hawq,stanlyxiang/incubator-hawq,wengyanqing/incubator-hawq,lavjain/incubator-hawq,outofmem0ry/incubator-hawq