title: rest_api_init event not fired
body: <p>I am trying to run custom plugin on wp 4.7.4 . Below is my simple plugin </p>
  
  <pre><code>add_action( 'rest_api_init', 'register_routes');
  
  
  function register_routes() {
     register_rest_route( 'taxonomy-manager/v1', '/taxonomies/(P&lt;taxonomy_type&gt;[a-zA-Z]+)', array(
     'methods' =&gt; 'GET',
     'callback' =&gt; 'get_or_insert'
    ) );
  } 
  
  function get_or_insert( WP_REST_Request $request ) {
  
     $parameters = $request-&gt;get_params();
  
     return $parameters;
  
  }
  </code></pre>
  
  <p>When I request <code>wp-json</code> endpoint I see no plugin route there. Plugin was successfully activated. Have I missed something ? Does above plugin (or similar one based on <code>rest_api_init</code> event) works for anybody else ?  Thanks.</p>