fix pidfile, pid is num use '/proc + string(pid)' can't found it
fix pidfile, pid is num use '/proc + string(pid)' can't found it

Signed-off-by: mingqing <3f165d5ea18b818b62076b63fefe68aa3b61adc9@cyou-inc.com>

aditirajagopal/docker,aditirajagopal/docker,aditirajagopal/docker