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/vat2/plugin.c b/src/vat2/plugin.c
index 6b6d55a..3ad8705 100644
--- a/src/vat2/plugin.c
+++ b/src/vat2/plugin.c
@@ -165,7 +165,7 @@
 		{
 		  res = -1;
 		  vec_free (plugin_name);
-		  _vec_len (plugin_info) = vec_len (plugin_info) - 1;
+		  vec_set_len (plugin_info, vec_len (plugin_info) - 1);
 		  continue;
 		}
 	      clib_memset (pi, 0, sizeof (*pi));