flink日志目录修改

https://stackoverflow.com/questions/34633225/how-to-change-flinks-log-directory

env:
  log:
    dir: /var/log/flink

英文版的官网才有(log4j2的配置)：
https://nightlies.apache.org/flink/flink-docs-master/docs/deployment/advanced/logging/