Ensure the age_add variable is properly initialised

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2259)
diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index 3695c75..cd87194 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -2212,7 +2212,7 @@
 {
     int al;
     unsigned int ticklen;
-    unsigned long ticket_lifetime_hint, age_add;
+    unsigned long ticket_lifetime_hint, age_add = 0;
     unsigned int sess_len;
     RAW_EXTENSION *exts = NULL;