Set TCP keepalive on inbound clusterbus connections (#9230)

Set TCP keepalive on inbound clusterbus connections to prevent memory leak

src/cluster.c

@@ -736,6 +736,7 @@ void clusterAcceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
             return;
         }
         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);