Address deprecation warning for start YARN 2.x

[arvindshmicrosoft]

Fixes #291

[ctubbsii]

Thanks, @arvindshmicrosoft . A quick note:

I see that you created #291, and then exactly one minute later, submitted this PR #292 to fix it. Some projects might require a separate issue, but we don't require that. GitHub treats PRs as issues, so it's fine to just do the PR in situations like this.

Sometimes, it can be helpful to have a separate issue, as in:

• reporting a bug immediately, and troubleshooting later,
• discussion would be useful before beginning work,
• reporting a bug for somebody else to work on,
• creating a parent task for tracking multiple sub-tasks,
• creating one issue, but different PRs for different branches,
• etc.

But, it's not always helpful, so we don't require it. A PR is fine by itself. Use your discretion, of course. 😺