Add state retrieved to ipavault to retrieve vault stored data.

This patch adds support for retrieving data stored in an IPA vault by
adding a new valid state for ipavault: `retrieved`.

To allow the retrieval of data from assymetric vaults, the attributes
`private_key`, `private_key_files` and `out` were also added to the
module.

The private key files, `private.pem`, should be paired with the already
existing `public.pem` public key files.

Tests were updated to reflect changes and two new playbooks were added:

    playbooks/vault/retrive-data-asymmetric-vault.yml
    playbooks/vault/retrive-data-symmetric-vault.yml

README-vault.md

@@ -144,8 +144,7 @@ Example playbook to retrieve vault data from a symmetric vault:
       name: symvault
       username: admin
       password: SomeVAULTpassword
-      retrieve: true
-      action: member
+      state: retrieved
 ```
 
 Example playbook to make sure vault data is absent in a symmetric vault:
@@ -180,6 +179,9 @@ Example playbook to make sure vault is absent:
       name: symvault
       username: admin
       state: absent
+    register: result
+  - debug:
+      msg: "{{ result.data }}"
 ```
 
 Variables
@@ -199,7 +201,7 @@ Variable | Description | Required
 `public_key ` \| `vault_public_key` \| `ipavaultpublickey` | Base64 encoded vault public key. | no
 `public_key_file` \| `vault_public_key_file` | Path to file with public key. | no
 `private_key `\| `vault_private_key` | Base64 encoded vault private key. Used only to retrieve data. | no
-`private_key_file` \| `vault_private_key_file` | Path to file with private key. | no
+`private_key_file` \| `vault_private_key_file` | Path to file with private key. Used only to retrieve data. | no
 `salt` \| `vault_salt` \| `ipavaultsalt` | Vault salt. | no
 `vault_type` \| `ipavaulttype` | Vault types are based on security level. It can be one of `standard`, `symmetric` or `asymmetric`, default: `symmetric` | no
 `user` \| `username` | Any user can own one or more user vaults. | no
@@ -211,9 +213,21 @@ Variable | Description | Required
 `data` \|`vault_data` \| `ipavaultdata` | Data to be stored in the vault. | no
 `in` \| `datafile_in` | Path to file with data to be stored in the vault. | no
 `out` \| `datafile_out` | Path to file to store data retrieved from the vault. | no
-`retrieve` | If set to True, retrieve data stored in the vault. (bool) | no
 `action` | Work on vault or member level. It can be on of `member` or `vault` and defaults to `vault`. | no
-`state` | The state to ensure. It can be one of `present` or `absent`, default: `present`. | no
+`state` | The state to ensure. It can be one of `present`, `absent` or `retrieved`, default: `present`. | no
+
+
+Return Values
+=============
+
+ipavault
+--------
+
+There is only a return value if `state` is `retrieved`.
+
+Variable | Description | Returned When
+-------- | ----------- | -------------
+`data` | The data stored in the vault. | If `state` is `retrieved`.
 
 
 Notes