ffserver: do not ignore ff_socket_nonblock return

Should fix FFmpeg Coverity Scan issues #732180 & #732182
Signed-off-by: Reynaldo H. Verdejo Pinochet <r.verdejo@sisa.samsung.com>

ffserver.c

@@ -572,7 +572,9 @@ static int socket_open_listen(struct sockaddr_in *my_addr)
         closesocket(server_fd);
         return -1;
     }
-    ff_socket_nonblock(server_fd, 1);
+
+    if (ff_socket_nonblock(server_fd, 1) < 0)
+        av_log(NULL, AV_LOG_WARNING, "ff_socket_nonblock failed\n");
 
     return server_fd;
 }
@@ -826,7 +828,8 @@ static void new_connection(int server_fd, int is_rtsp)
         http_log("error during accept %s\n", strerror(errno));
         return;
     }
-    ff_socket_nonblock(fd, 1);
+    if (ff_socket_nonblock(fd, 1) < 0)
+        av_log(NULL, AV_LOG_WARNING, "ff_socket_nonblock failed\n");
 
     if (nb_connections >= nb_max_connections) {
         http_send_too_busy_reply(fd);