http: do not rely on the 'agentRemove' event
Do not use the 'agentRemove'
event to null socket._httpMessage
as
that event is public and can be used to not keep a request in the agent.
Fixes: https://github.com/nodejs/node/issues/20690
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines