Set SO_KEEPALIVE on client sockets if configured to do so.

src/networking.c

@@ -59,6 +59,8 @@ redisClient *createClient(int fd) {
     if (fd != -1) {
         anetNonBlock(NULL,fd);
         anetEnableTcpNoDelay(NULL,fd);
+        if (server.tcpkeepalive)
+            anetKeepAlive(NULL,fd,server.tcpkeepalive);
         if (aeCreateFileEvent(server.el,fd,AE_READABLE,
             readQueryFromClient, c) == AE_ERR)
         {