Ability of slave to announce arbitrary ip/port to master.

This feature is useful, especially in deployments using Sentinel in
order to setup Redis HA, where the slave is executed with NAT or port
forwarding, so that the auto-detected port/ip addresses, as listed in
the "INFO replication" output of the master, or as provided by the
"ROLE" command, don't match the real addresses at which the slave is
reachable for connections.

src/networking.c

@@ -109,6 +109,7 @@ client *createClient(int fd) {
     c->repl_ack_off = 0;
     c->repl_ack_time = 0;
     c->slave_listening_port = 0;
+    c->slave_ip[0] = '\0';
     c->slave_capa = SLAVE_CAPA_NONE;
     c->reply = listCreate();
     c->reply_bytes = 0;