Explictly close the TPLink SmartDevice protocol on unload

[bdraco]

Proposed change

• There is a destructor that will eventually do this when
  the object gets gc. Its better to explicitly do it at
  unload so any errors are not hidden away when the destructor
  eventually runs.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
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• Tests have been added to verify that the new code works.

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  Updated and included derived files by running: python3 -m script.hassfest.
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  Updated by running python3 -m script.gen_requirements_all.
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[probot-home-assistant]

Hey there @rytilahti, @TheGardenMonkey, mind taking a look at this pull request as it has been labeled with an integration (tplink) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[rytilahti]

LGTM after the tests pass 👍