Merge branch 'handle-injector-swarm-growth'.
This includes some enhancements to cope with transitory addresses appearing in injector and bridge swarms, be they fake (attackers or BitTorrent spy nodes) or genuine (like clients no longer available), as everything seen in the swarms was never forgotten by the client, which caused the local view of the swarm to grow indefinitely, causing issues like legitimate injectors never getting picked for pinging in long-running clients. - Use an LRU cache for swarm entries in the client (to eventually drop spurious entries). - Also, do not ping injectors if a connection to one of them was successfully established while waiting for the next ping round. Further refinement in swarm and ping handling paramenters may be needed, as well as more sophisticated handling of the ping process.