Adjust playbooks for Ansible 2.4 import changes

Ansible 2.4 changes the way includes work. Now you have to use "import"
for playbooks and tasks that are static, and "include" for those that
are dynamic (ie, those that use variables, loops, etc).

See: http://docs.ansible.com/ansible/devel/playbooks_reuse_includes.html

roles/nginx/tasks/main.yml

@@ -34,7 +34,7 @@
   file: path=/var/cache/nginx/cached/fastcgi state=directory owner=nginx group=nginx mode=0755
   tags: nginx
 
-- include: vhosts.yml
+- import_tasks: vhosts.yml
   when: nginx_vhosts is defined
   tags: nginx
 

roles/nginx/tasks/vhosts.yml

@@ -32,7 +32,7 @@
   with_items: "{{ nginx_vhosts }}"
   tags: wordpress
 
-- include: letsencrypt.yml
+- import_tasks: letsencrypt.yml
   when: use_letsencrypt is defined and use_letsencrypt == True
   tags: letsencrypt