Change RedpandaContainer startup script path

[lorenzobenvenuti]

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

[lorenzobenvenuti]

Since the change was pretty strightforward, I went ahead and created a PR. Please lmk what you think.

Thanks,

lorenzo