logrotate and log to specific file

logrotate后期可以自己修改，如果不存在则会自动创建
并且goagent log输出到指定文件
Check if /etc/logrotate.d exists

检测是否存在目录/etc/logrotate.d
Merge pull request #81 from tkisme/3.0

logrotate and log to specific file