bugfix: dir_exists is never awaited

[stdll00]

Accoding to https://github.com/jupyter-server/jupyter_server/blob/master/jupyter_server/services/contents/manager.py#L579 , AsyncContentsManager. dir_exists can be async function, but never awaited in test case.

Background: I implemented subclass of AsyncContentsManager, but it not passed this testcase.

[welcome]

Thanks for submitting your first pull request! You are awesome! 🤗

If you haven't done so already, check out Jupyter's Code of Conduct. Also, please make sure you followed the pull request template, as this will help us review your contribution more quickly.

You can meet the other Jovyans by joining our Discourse forum. There is also a intro thread there where you can stop by and say Hi! 👋

Welcome to the Jupyter community! 🎉

[codecov-commenter]

Codecov Report

Merging #597 (19aa87b) into master (f944deb) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #597      +/-   ##
==========================================
- Coverage   77.40%   77.34%   -0.06%     
==========================================
  Files         110      110              
  Lines       10250    10250              
  Branches     1257     1257              
==========================================
- Hits         7934     7928       -6     
- Misses       1918     1926       +8     
+ Partials      398      396       -2     

Impacted Files	Coverage Δ
...ter_server/tests/services/contents/test_manager.py	96.95% <100.00%> (ø)
jupyter_server/services/kernels/kernelmanager.py	79.79% <0.00%> (-2.06%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f944deb...19aa87b. Read the comment docs.

[blink1073]

Thank you!

[blink1073]

Test failures are unrelated (nbconvert tests are flaky).

[welcome]

Congrats on your first merged pull request in this project! 🎉

Thank you for contributing, we are very proud of you! ❤️