🐛 fix conn dropped issue occurring in 2.11.900

[Ousret]

Fix jawah/niquests#160

[Ousret]

there is edge cases we'll need to answer

FAILED test/with_dummyserver/test_socketlevel.py::TestSocketClosing::test_recovery_when_server_closes_connection - urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=40719): Max retries exceeded with url: / (Caused by ProtocolError("can't handle event type ConnectionClosed when role=SERVER and state=SEND_RESPONSE"))
FAILED test/with_dummyserver/test_socketlevel.py::TestProxyManager::test_retries - urllib3.exceptions.ProtocolError: can't handle event type ConnectionClosed when role=SERVER and state=SEND_RESPONSE

not urgent, but needed.