feat(fluentd): use tini; add override for entrypoint

[Boojapho]

Closes #373

Closes #374

• Forces use of tini in all cases
• Allows user to override entrypoint script if desired

[Boojapho]

@dioguerra @edsiper I have quite a few PRs that need review. Let me know if you have time to review them.

[tspearconquest]

Hi @Boojapho - I had some luck with getting a pull request merged by pinging in their slack recently. I'd like to see this merged, I thought I'd let you know you might want to rebase your pulls and increase the chart version and try to reach them on slack to approve this and your others.