add certbot-nginx support, remove ubuntu 16.04

tasks/include-vars.yml

@@ -1,8 +0,0 @@
----
-- name: Load a variable file based on the OS type, or a default if not found.
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "{{ ansible_distribution }}-{{ ansible_distribution_version }}.yml"
-    - "{{ ansible_distribution }}.yml"
-    - "{{ ansible_os_family }}.yml"
-    - "default.yml"

tasks/install-with-package.yml

@@ -4,4 +4,4 @@
 
 - name: Set Certbot script variable.
   set_fact:
-    certbot_script: "{{ certbot_package }}"
+    certbot_script: "certbot"

tasks/main.yml

@@ -1,6 +1,4 @@
 ---
-- import_tasks: include-vars.yml
-
 - import_tasks: setup-RedHat.yml
   when: ansible_os_family == 'RedHat'