dynamicproxy: Block non-local Redis connections

At the moment, the Redis server managing the proxy configuration is
firewalled from the outside with iptables.  This change moves that
restriction into the Redis configuration itself.

Also, probaby for performance, in production Redis servers don't
automatically reread their configuration when it changes.  This
behaviour is not useful for proxies and thus this change notifies the
Redis server on proxy instances of changes in its configuration.

Change-Id: Iefe0ce3dd66c116f2c996eed06d71144a0506572
Merge "dynamicproxy: Block non-local Redis connections" into production