Pin nodejs package to upstream repo

In the case where a node_version is less than what's in the distro,
we'll wind up installing distro packages instead of upstream packages
which will either fail due to binary path naming issues, or succeed but
install a different version of nodejs than was requested.

Pin the package to the nodesource repo.

Put the file in as a template, as we should really update this role to
be able to optionally make use of a local mirror, in which case the file
will need to jinja.

Change-Id: If313d895a73bd2be7f598179a51b6485a37000ba

roles/install-nodejs/tasks/main.yaml

@@ -27,6 +27,17 @@
     update_cache: yes
   become: yes
 
+# Use template so that we can easily update this in the future to be able to
+# use a mirror location.
+- name: Pin NodeJS to nodesource apt repository
+  become: yes
+  template:
+    dest: /etc/apt/preferences.d/nodejs.pref
+    group: root
+    mode: 0644
+    owner: root
+    src: nodejs.pref.j2
+
 - name: Install NodeJS from nodesource
   package:
     name: nodejs

roles/install-nodejs/templates/nodejs.pref.j2

@@ -0,0 +1,3 @@
+Package: nodejs
+Pin: origin deb.nodesource.com
+Pin-Priority: 900