send SNI for federation requests

synapse/app/client_reader.py

synapse/app/event_creator.py

synapse/app/federation_reader.py

synapse/app/federation_sender.py

synapse/app/frontend_proxy.py

synapse/app/homeserver.py

synapse/app/media_repository.py

synapse/app/user_dir.py

synapse/config/tls.py

synapse/crypto/context_factory.py

synapse/crypto/keyclient.py

synapse/crypto/keyring.py

synapse/http/endpoint.py

synapse/http/matrixfederationclient.py

tests/utils.py