Allow worker.*.maxContainers to be 0

[KoltesDigital]

Why do we need this PR?

worker.*.maxContainers documentation states it's 250 by default, and 0 is unlimited. However, setting it to 0 makes the template skip the env var, thus taking its default value.

Changes proposed in this pull request

Take into account that they can be to set 0.

Contributor Checklist

• Which branch are you merging into?
  • master is for changes related to the current release of the concourse/concourse:latest image and should be good to publish immediately

Reviewer Checklist

This section is intended for the core maintainers only, to track review progress. Please do not
fill out this section.

• Code reviewed
• Topgun tests run
• Back-port if needed
• Is the correct branch targeted? (master or dev)

[taylorsilva]

LGTM - I had to double check that setting it to zero does mean unlimited at the binary level, and it does. Good find!

[taylorsilva]

@KoltesDigital Could you do the DCO signoff please? You have to amend your commit and add Signed-off-by: Author Name <[email protected]>. I think you can do git commit --amend -s to have git do it automatically for you 🙏