vlib: fix coverity warning / real bug

The path must be next-to-impossible to hit, because the code has been
wrong for at least 5 years.

Type: fix

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I23b8c4e1631827e7931f353c561c1e19c596c598
diff --git a/src/vlib/cli.c b/src/vlib/cli.c
index 467d1f7..bb6c574 100644
--- a/src/vlib/cli.c
+++ b/src/vlib/cli.c
@@ -1217,7 +1217,7 @@
 		    vec_len (p->sub_rules));
       vec_add2 (p->sub_rules, sr, 1);
       sr->name = sub_name;
-      sr->rule_index = q[0];
+      sr->rule_index = sr - p->sub_rules;
       sr->command_index = child_index;
       return;
     }