Update net_asyncio.py

[dpineiden]

Reason for the change If applicable, link the related issue/bug report or write down in few sentences the motivation.

Description A clear and concise description of what did you changed and why.

Code examples If applicable, add code examples to help explain your changes.

Checklist

• [ ] I have read and agreed to the RethinkDB Contributor License Agreement

References Anything else related to the change e.g. documentations, RFCs, etc.

At the python doc, a closing of async socket has that two lines:

self.streamwriter.close()
await self.streamwriter.wait_closed()

In my case, despite closing connections, those are not closing and the number of open cons are increasing (without second line)

[dpineiden]

https://docs.python.org/es/3/library/asyncio-stream.html

[codeclimate[bot]]

Code Climate has analyzed commit 975e22a3 and detected 0 issues on this pull request.

View more on Code Climate.

[srh]

Sorry about the needless notification -- I unclosed because I realized my issue or PR maintenance would step on the real maintainers' toes. And there is a legitimate wait_closed change...