Align SSL_SESSION_up_ref with OpenSSL.

Only X509_up_ref left (it's still waiting on a few external callers).

BUG=89

Change-Id: Ia2aec2bb0a944356cb1ce29f3b58a26bdb8a9977
Reviewed-on: https://boringssl-review.googlesource.com/9141
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/handshake_server.c b/ssl/handshake_server.c
index c47ba67..a6d26d1 100644
--- a/ssl/handshake_server.c
+++ b/ssl/handshake_server.c
@@ -487,7 +487,8 @@
 
         SSL_SESSION_free(ssl->s3->established_session);
         if (ssl->session != NULL) {
-          ssl->s3->established_session = SSL_SESSION_up_ref(ssl->session);
+          SSL_SESSION_up_ref(ssl->session);
+          ssl->s3->established_session = ssl->session;
         } else {
           ssl->s3->established_session = ssl->s3->new_session;
           ssl->s3->established_session->not_resumable = 0;