IPv6 support for endpoint.py
IPv6 support for endpoint.py

Similar to https://github.com/matrix-org/synapse/pull/1689, but for endpoint.py
matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse,TribeMedia/synapse,matrix-org/synapse