SEC-79: Install nginx from their ppa

This change allows us to install nginx from nginx's ppa as per their
instructions at http://nginx.org/en/linux_packages.html

playbooks/roles/nginx/defaults/main.yml

@@ -49,6 +49,7 @@ NGINX_SERVER_HTML_FILES:
 
 
 
+
 nginx_app_dir: "{{ COMMON_APP_DIR }}/nginx"
 nginx_data_dir: "{{ COMMON_DATA_DIR }}/nginx"
 nginx_server_static_dir: "{{ nginx_data_dir }}/server-static"
@@ -60,7 +61,6 @@ nginx_user: root
 nginx_htpasswd_file: "{{ nginx_app_dir }}/nginx.htpasswd"
 nginx_default_sites: []
 nginx_debian_pkgs:
-  - nginx
   - python-passlib
 
 NGINX_EDXAPP_ENABLE_S3_MAINTENANCE: False

playbooks/roles/nginx/tasks/main.yml

@@ -33,8 +33,37 @@
     - install
     - install:configuration
 
-- name: Install nginx packages
-  apt: pkg={{','.join(nginx_debian_pkgs)}} state=present
+- name: Install needed packages
+  apt: pkg={{ item }} state=present
+  notify: restart nginx
+  with_items: nginx_debian_pkgs
+  tags:
+    - install
+    - install:system-requirements
+
+- name: Add apt key
+  apt_key:
+    url: http://nginx.org/keys/nginx_signing.key
+    state: present
+  notify: restart nginx
+  tags:
+    - install
+    - install:system-requirements
+
+- name: Add nginx repository
+  apt_repository:
+    repo: deb http://nginx.org/packages/ubuntu/ {{ ansible_distribution_release }} nginx
+    state: present
+  notify: restart nginx
+  tags:
+    - install
+    - install:system-requirements
+
+- name: Install the nginx package
+  apt:
+    name: nginx
+    state: latest
+    update_cache: yes
   notify: restart nginx
   tags:
     - install