fix: Shutdown callback is not passed from provider to client

[pigulla]

Pass the optional shutdown callback from the Provider through to the Client.

fix #117

[parse-github-assistant[bot]]

I will reformat the title to use the proper commit message syntax.

[parse-github-assistant[bot]]

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[mtrezza]

@dplewis Would you want to review this?

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (5bc179d) 93.53% compared to head (dbe0821) 93.53%.

:exclamation: Current head dbe0821 differs from pull request most recent head c04174b. Consider uploading reports for the commit c04174b to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #118 +/- ## ======================================= Coverage 93.53% 93.53% ======================================= Files 23 23 Lines 588 588 ======================================= Hits 550 550 Misses 38 38 ``` | [Impacted Files](https://app.codecov.io/gh/parse-community/node-apn/pull/118?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community) | Coverage Δ | | |---|---|---| | [lib/provider.js](https://app.codecov.io/gh/parse-community/node-apn/pull/118?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community#diff-bGliL3Byb3ZpZGVyLmpz) | `100.00% <100.00%> (ø)` | |

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[dplewis]

@mtrezza This looks good. Client does have a shutdown function that accepts a callback

https://github.com/parse-community/node-apn/blob/master/lib/client.js#L305-L306

[parseplatformorg]

🎉 This change has been released in version 5.2.2