62c304ea48 tests: Allow closed http server in assert_start_raises_init_error (Chun Kuan Lee)
Pull request description:
The rpc handler may be unregistered when http server haven't been closed yet. So it may be allowable to get -342 `non-JSON HTTP response with \'%i %s\' from server` (503 Service Unavailable) See https://ci.appveyor.com/project/DrahtBot/bitcoin/build/master.2001. It shows "Rejecting request while shutting down" between "RPC stopped" and "Stopped HTTP server"
Backport of Core PR14413