Change RedpandaContainer startup script path

Hi,

we're running Testcontainers in Openshift using Kubedock; when using RedpandaContainer, our tests break because , after the container is started, the actual startup script is copied to / which is not writable by the redpanda user. I think we could safely switch to another directory, for example /var/lib/redpanda (btw I see other libraries are doing the same, see here).
I realize we have a pretty unique setup but the change should be pretty simple and probably using a directory owned by the user that runs the container could prevent issues in other environments too.
If you think it's feasible I can work on a PR.

Thanks,

lorenzo

首先定位 RedpandaContainer 的实现，并检查容器启动后其启动脚本会被复制到哪里。检查 issue 中描述的 OpenShift 和 Kubedock 设置下现有的容器行为。当脚本被放置在 redpanda 用户可写的目录中，并且受影响的测试不再失败时，即表示完成。