Fix a memory leak in n_ssl3_mac

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5648)

ssl/record/ssl3_record.c

diff --git a/ssl/record/ssl3_record.c b/ssl/record/ssl3_record.c
index 5bfbaf9..4ffc842 100644
--- a/ssl/record/ssl3_record.c
+++ b/ssl/record/ssl3_record.c
@@ -1256,7 +1256,7 @@
             || EVP_DigestUpdate(md_ctx, ssl3_pad_2, npad) <= 0
             || EVP_DigestUpdate(md_ctx, md, md_size) <= 0
             || EVP_DigestFinal_ex(md_ctx, md, &md_size_u) <= 0) {
-            EVP_MD_CTX_reset(md_ctx);
+            EVP_MD_CTX_free(md_ctx);
             return 0;
         }