Shutdown kernels/terminals on api/shutdown

[martinRenou]

Fix #578

[codecov-commenter]

Codecov Report

Merging #579 (4c59367) into master (49d5772) will increase coverage by 0.04%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master     #579      +/-   ##
==========================================
+ Coverage   77.46%   77.51%   +0.04%     
==========================================
  Files         110      110              
  Lines       10184    10188       +4     
  Branches     1100     1100              
==========================================
+ Hits         7889     7897       +8     
+ Misses       1907     1901       -6     
- Partials      388      390       +2     

Impacted Files	Coverage Δ
jupyter_server/services/shutdown.py	70.00% <50.00%> (-7.78%)	⬇️
jupyter_server/base/handlers.py	64.30% <66.66%> (+0.01%)	⬆️
jupyter_server/services/kernels/kernelmanager.py	81.84% <0.00%> (+2.05%)	⬆️

---

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 49d5772...4c59367. Read the comment docs.

[davidbrochart]

Maybe we should do the same as when shutting down the server with Ctrl-C?

jupyter_server/jupyter_server/serverapp.py

Lines 2631 to 2639 in 52e1095

	async def _cleanup(self):
	"""General cleanup of files, extensions and kernels created
	by this instance ServerApp.
	"""
	self.remove_server_info_file()
	self.remove_browser_open_files()
	await self.cleanup_extensions()
	await self.cleanup_kernels()
	await self.cleanup_terminals()

[kevin-bates]

Thanks @martinRenou - These changes look good and in fact resolve a regression issue.