acl-plugin: fix coverity error 171135

The code path which sets the sw_if_index aimed to restrict the output
did not set the flag to trigger that output.

Change-Id: I0a1a3977fdddbce9a276960df43fed745d099ca0
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

src/plugins/acl/acl.c

@@ -2076,6 +2076,8 @@ acl_show_aclplugin_fn (vlib_main_t * vm,
       u32 show_bihash_verbose = 0;
 
       if (unformat (input, "acl")) {
+        show_acl_hash_info = 1;
+        /* mask-type is handy to see as well right there */
         show_mask_type = 1;
         unformat (input, "index %u", &acl_index);
       } else if (unformat (input, "applied")) {