Convert SSL_SESSION* functions to use const getters

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Stephen Henson <steve@openssl.org>
diff --git a/test/handshake_helper.c b/test/handshake_helper.c
index 07615ad..c4b14e7 100644
--- a/test/handshake_helper.c
+++ b/test/handshake_helper.c
@@ -699,7 +699,7 @@
     int client_turn = 1;
     connect_phase_t phase = HANDSHAKE;
     handshake_status_t status = HANDSHAKE_RETRY;
-    unsigned char* tick = NULL;
+    const unsigned char* tick = NULL;
     size_t tick_len = 0;
     SSL_SESSION* sess = NULL;
     const unsigned char *proto = NULL;