su instead of su-exec

[synergiator]

su-exec is a third-party Alpine package i.e. not a part of GNU neither Apache project:
https://github.com/ncopa/su-exec

Therefore, I thought maybe it can work just with su as well

https://github.com/bigdata-central/zookeeper-docker/blob/ubuntu/3.4.10/docker-entrypoint.sh

(thanks to DevOps SE https://devops.stackexchange.com/questions/2526/interference-of-docker-cmd-with-su-works-with-su-exec-but-not-with-su)

[31z4]

The main motivation for not using su is that it spawns a child process

$ docker run -it --rm zookeeper su -c 'ps aux'
PID   USER     TIME   COMMAND
    1 root       0:00 ash -c ps aux
    8 root       0:00 ps aux

while su-exec does not

$ docker run -it --rm zookeeper su-exec root ps aux
PID   USER     TIME   COMMAND
    1 root       0:00 ps aux

And as it's said in https://github.com/tianon/gosu and https://github.com/ncopa/su-exec this might introduce some TTY and signal-forwarding issues.