Plumb puppetmaster through ansible task

The previous change to make the puppetmaster configurable in the ansible
playbook omitted passing through the parameter in the task.  Also, add
the parameter to the module docs.

Change-Id: I6bcd58803fd11c3d64608ea1d9fca269042936b4

library/config_management/puppet

@@ -30,6 +30,10 @@ options:
       - How long to wait for I(puppet) to finish.
     required: false
     default: 30m
+  puppetmaster:
+    description:
+      - The hostname of the puppetmaster to contact.
+    required: true
   show_diff:
     description:
       - Should puppet return diffs of changes applied. Defaults to off to avoid leaking secret changes by default.

roles/puppet/tasks/main.yml

@@ -1,3 +1,4 @@
 ---
 - name: run puppet
   puppet:
+    puppetmaster: "{{puppetmaster}}"