fix: add ctx test handlers, fix hanging channel, fix typo

[winslowdibona]

This PR attempts to address several issues:

1. Adds support for kong.ctx.shared.get and kong.ctx.shared.set in the test module
   • Issue #171
2. Fixes a typo finnished -> finished
3. Includes changes introduced by @jakeslee in PR 170 to fix issue with hanging channel in kong.response.exit
   • Issue #169

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[winslowdibona]

@jakeslee I've included your changes I saw on PR 170 in mine as I was facing the same issue when testing locally.

[winslowdibona]

@fffonion @gszr Who should contributors reach out to when seeking reviews/approval on pull requests? I ask you all
because I see your comments/commits on recent PRs

[gszr]

@winslowdibona - Thank you for the PR!