tls: add openssl engine

Change-Id: I6c215858d2c9c620787632b570950b15274c0df2
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/session-apps/echo_client.h b/src/vnet/session-apps/echo_client.h
index 4ae63ec..5712da5 100644
--- a/src/vnet/session-apps/echo_client.h
+++ b/src/vnet/session-apps/echo_client.h
@@ -64,7 +64,7 @@
   u32 connections_per_batch;		/**< Connections to rx/tx at once */
   u32 private_segment_count;		/**< Number of private fifo segs */
   u32 private_segment_size;		/**< size of private fifo segs */
-
+  u32 tls_engine;			/**< TLS engine mbedtls/openssl */
   /*
    * Test state variables
    */