Fix clang warnings in applications

Some fd would be used uninitialized if we goto exit early.
diff --git a/programs/ssl/ssl_fork_server.c b/programs/ssl/ssl_fork_server.c
index 3b24b31..e116119 100644
--- a/programs/ssl/ssl_fork_server.c
+++ b/programs/ssl/ssl_fork_server.c
@@ -96,7 +96,7 @@
 {
     int ret, len, cnt = 0, pid;
     int listen_fd;
-    int client_fd;
+    int client_fd = -1;
     unsigned char buf[1024];
     const char *pers = "ssl_fork_server";