Fix memory leak in ssl3_send_client_key_exchange error handling.

Change-Id: I0f0d7a3d4cb6448582ae4945e732611bb9bf5d9f
Reviewed-on: https://boringssl-review.googlesource.com/2231
Reviewed-by: Adam Langley <agl@google.com>

ssl/s3_clnt.c

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 36f82bc..54dbbd7 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1943,6 +1943,8 @@
 				(pkey->pkey.rsa == NULL))
 				{
 				OPENSSL_PUT_ERROR(SSL, ssl3_send_client_key_exchange, ERR_R_INTERNAL_ERROR);
+				if (pkey != NULL)
+					EVP_PKEY_free(pkey);
 				goto err;
 				}
 			rsa=pkey->pkey.rsa;