Set TCP keepalive on inbound clusterbus connections (#9230)

Set TCP keepalive on inbound clusterbus connections to prevent memory leak

(cherry picked from commit f03af47a34)

src/cluster.c

@@ -707,6 +707,7 @@ void clusterAcceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
         }
         connNonBlock(conn);
         connEnableTcpNoDelay(conn);
+        connKeepAlive(conn,server.cluster_node_timeout * 2);
 
         /* Use non-blocking I/O for cluster messages. */
         serverLog(LL_VERBOSE,"Accepting cluster node connection from %s:%d", cip, cport);