make all passwords alphanumeric, use defaults instead of vars inside roles for precedence

Change-Id: I9d521d2521a1f208addec3810b13f8c030f9dcaf
diff --git a/roles/compute-node/vars/main.yml b/roles/compute-node/defaults/main.yml
similarity index 96%
rename from roles/compute-node/vars/main.yml
rename to roles/compute-node/defaults/main.yml
index 5accf44..8bb3905 100644
--- a/roles/compute-node/vars/main.yml
+++ b/roles/compute-node/defaults/main.yml
@@ -1,7 +1,9 @@
+---
+
 pub_ssh_key: "{{ lookup('file', '/etc/maas/.ssh/cord_rsa.pub') }}"
 
 compute_node:
-    password: "{{password_compute_node | default(lookup('password', 'passwords/compute_node.txt'))}}"
+    password: "{{password_compute_node | default(lookup('password', 'passwords/compute_node.txt chars=ascii_letters,digits'))}}"
     fabric:
         include:
             names: "{{ fabric_include_names | default(omit) }}"