Make redhat_subscription parameters optional

Using default(omit), parameters not part of environment won't be sent to
the module, so fully ignored.
Indeed, username/password/state/autosubscribe are all optional.

Change-Id: I3a81cdaccd2d90a43dec95d21b26d9ea503ed313

README.md

@@ -14,8 +14,8 @@ Role Variables
 
 | Name              | Default Value       | Description          |
 |-------------------|---------------------|----------------------|
-| `rhn_username` | `{{ lookup('env', 'RHN_USERNAME') }}` | Red Hat Portal username. |
-| `rhn_password` | `{{ lookup('env', 'RHN_PASSWORD') }}` | Red Hat Portal password. |
+| `rhn_username` | No default | Red Hat Portal username. |
+| `rhn_password` | No default | Red Hat Portal password. |
 | `rhsub_state` | `enable` | Whether to enable or disable a Red Hat subscription. |
 | `rhsub_autosubscribe` | `yes` | Whether or not to autosubscibe to available repositories. |
 | `rhsub_repos` | `[undefined]` | If defined, the list of repositories to enable or disable. See `defaults/main.yml` for examples. |

defaults/main.yml

@@ -1,5 +1,6 @@
-rhn_username: "{{ lookup('env', 'RHN_USERNAME') }}"
-rhn_password: "{{ lookup('env', 'RHN_PASSWORD') }}"
+# These parameters aren't required, so no default is provided:
+# rhn_username: joe
+# rhn_password: secrete
 
 rhsub_state: present                      # present or absent
 rhsub_autosubscribe: True

tasks/main.yml

@@ -17,10 +17,10 @@
 
 - name: Manage Red Hat subscription
   redhat_subscription:
-    username: "{{ rhn_username }}"
-    password: "{{ rhn_password }}"
-    state: "{{ rhsub_state }}"
-    autosubscribe: "{{ rhsub_autosubscribe }}"
+    username: "{{ rhn_username|default(omit) }}"
+    password: "{{ rhn_password|default(omit) }}"
+    state: "{{ rhsub_state|default(omit) }}"
+    autosubscribe: "{{ rhsub_autosubscribe|default(omit) }}"
   tags:
     - rhsub
     - rhsub_register