[CORD-1530]
Make config file directory creation using become an optional step
Cleanup various incongruities in defaults

Change-Id: I6fb77ab1ccdf08a18468adbc59474f94d603fc11
diff --git a/prep-headnode-playbook.yml b/prep-headnode-playbook.yml
index bca4959..ffdb758 100644
--- a/prep-headnode-playbook.yml
+++ b/prep-headnode-playbook.yml
@@ -54,7 +54,7 @@
   hosts: head
   become: yes
   roles:
-    - { role: apt-cacher-ng, when: use_apt_cache }
+    - { role: apt-cacher-ng, when: use_apt_cache | default(True) }
 
 - name: Install apache proxy
   hosts: head