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/vlib/cli.c b/src/vlib/cli.c
index b7c4c00..dcabe8d 100644
--- a/src/vlib/cli.c
+++ b/src/vlib/cli.c
@@ -617,7 +617,7 @@
 		      vec_add1 (c_error->what, 0);
 		      ed->err = elog_string (vlib_get_elog_main (),
 					     (char *) c_error->what);
-		      _vec_len (c_error->what) -= 1;
+		      vec_dec_len (c_error->what, 1);
 		    }
 		  else
 		    ed->err = elog_string (vlib_get_elog_main (), "OK");
@@ -1179,7 +1179,7 @@
 
   /* Remove any extra space at end. */
   if (l > 0 && s[l - 1] == ' ')
-    _vec_len (s) -= 1;
+    vec_dec_len (s, 1);
 
   *result = s;
   return index_of_last_space;