Audit settings change notifications aren't always being sent to couchdb

Steps to reproduce:

• Create any rbac user - say user1
• Add this user to the disabled_user list under audit settings as follows:

• As expected, we do observe a new couchdb system event log notifying the change from: {disabled_users,[]} to {disabled_users,[user1, local]}

curl -X GET -u Administrator:asdasd http://localhost:9000/events | jq '.events | .[] | select(.component == "views") | select(.node == "node1.couchbase.com")'

•  Remove this user from the disabled_users list and hit Save:

{}Expected:

There should be a new system event log specifying disabled_user list going from {disabled_users,[user1, local]} back to {disabled_users,[]}

           Observation:

          No new system event log is generated.

—

After putting some extra logging in the ns_config -> ns_couchdb -> couchdb codepaths, I can confirm that ns_server for some reason isn't pushing new "notable_change" "audit" events:

Just to confirm this behaviour, place a log message at
deps/ns_couchdb/src/cb_config_couch_sync.erl :

 handle_config_event({Key, _Value}) ->

     case is_notable_key(Key) of

         true ->

             ?log_info("pushing a notable change to gen_server. Key ~p", [Key]),

             ?MODULE ! {notable_change, Key};

         _ ->

             ok

     end;

 handle_config_event(_) ->

     ok.

The log message in the above snippet triggers for other audit changes, but doesn't get triggered under the following conditions:

1. When disabled_user list is changed from a non-empty to an empty list.
2. Also doesn't triggers if any of the views audit events are disabled.