Fixed bug related to heartbeat endpoints

... which could eventually occur when the device server runs on a host with multiple network interfaces. This bug was triggering API_EventTimeout errors generated by the KeepAliveThread with some network configurations. This bug occured when ZmqEventSubscriptionChange("info") command returned more than 2 values (meaning there are some alternate addresses) and when the 2 first returned value were some endpoints which were not available from the network where the client was running. Nevertheless, if the first 2 values were listing ip addresses which were accessible from the client network, the Tango events were still working as expected for this client.