[FIX] Prevent Monit template failures on non-standard Monit books

The https://github.com/phlipper/chef-monit cookbook does not define
the `monitrc` method, but uses the `monit_monitrc` LWRP.

See phlipper/chef-monit@2802d12

recipes/nginx.rb

@@ -41,7 +41,7 @@
   notifies :restart, 'service[nginx]', :immediately
 end
 
-if node.recipes.include?('monit') and defined?(:monitrc)
+if node.recipes.include?('monit') and respond_to?(:monitrc)
   monitrc "nginx.monitrc" do
     template_cookbook 'elasticsearch'
     source 'nginx.monitrc.conf.erb'