Fix file leak in test program

A similar bug was fixed earlier in ssl_server2, but we missed the fix
in ssl_client2.

programs/ssl/ssl_client2.c

@@ -619,6 +619,7 @@ static int nss_keylog_export( void *p_expkey,
         if( fwrite( nss_keylog_line, 1, len, f ) != len )
         {
             ret = -1;
+            fclose( f );
             goto exit;
         }