RDB Channel connections mistakenly discovered by Sentinel (#14728) (#14729)

Fix RDB Channel connections mistakenly discovered by Sentinel

During fullsync, if the main replication connection is interrupted, but
the rdbchannel connection is still active, it will be visible in the
"info replication" output. Currently, the rdbchannel connection does not
send `REPLCONF ip-address`, and in a meshed scenario, when the source IP
addresses of both connections differ, Sentinel will treat them as
separate replicas. This commit adds `REPLCONF ip-address` to rdbchannel
replica handshake if `server.slave_announce_ip` is enabled.

fixes: https://github.com/redis/redis/issues/14728

Co-authored-by: Ozan Tezcan <ozantezcan@gmail.com>

src/replication.c

@@ -3724,7 +3724,11 @@ static int rdbChannelSendHandshake(connection *conn, sds *err) {
 
     *err = sendCommand(conn, "REPLCONF", "capa", "eof", "rdb-only", "1",
                        "rdb-channel", "1", "main-ch-client-id", cid,
-                       "listening-port", buf, NULL);
+                       "listening-port", buf,
+                       server.slave_announce_ip ? "ip-address" : NULL,
+                       server.slave_announce_ip ? server.slave_announce_ip : NULL,
+                       NULL);
+    
     if (*err) {
         serverLog(LL_WARNING, "Error sending REPLCONF command to master in rdb channel handshake: %s", *err);
         return C_ERR;