vppinfra: make _vec_len() read-only

Use of _vec_len() to set vector length breaks address sanitizer.
Users should use vec_set_len(), vec_inc_len(), vec_dec_len () instead.

Type: improvement
Change-Id: I441ae948771eb21c23a61f3ff9163bdad74a2cb8
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vppinfra/socket.c b/src/vppinfra/socket.c
index a09a390..a3024ae 100644
--- a/src/vppinfra/socket.c
+++ b/src/vppinfra/socket.c
@@ -230,7 +230,7 @@
   else if (written > 0)
     {
       if (written == tx_len)
-	_vec_len (s->tx_buffer) = 0;
+	vec_set_len (s->tx_buffer, 0);
       else
 	vec_delete (s->tx_buffer, written, 0);
     }
@@ -278,7 +278,7 @@
     sock->flags |= CLIB_SOCKET_F_RX_END_OF_FILE;
 
 non_fatal:
-  _vec_len (sock->rx_buffer) += n_read - n_bytes;
+  vec_inc_len (sock->rx_buffer, n_read - n_bytes);
 
   return 0;
 }