Add ability to change apt/yum package state

The current method of installing the distribution packages required is
set in the tasks and cannot be changed by a deployer.

Currently the apt task always installs the latest package. This results
in unexpected binary changes when a deployer may simply be trying to
execute a configuration change.

This patch adds the ability for a deployer to change the desired state
so that the results are predictable.

Change-Id: I1708ca8285ffa2bbd1a989b187ef3c6d9dd005c2

defaults/main.yml

@@ -13,6 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Set the package install state for distribution packages
+# Options are 'present' and 'latest'
+rally_package_state: "latest"
+
 rally_system_group_name: rally
 rally_system_user_name: rally
 rally_system_user_comment: Rally System User

releasenotes/notes/package-state-63a870de53dd5cd8.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - The os_rally role now supports the ability to configure whether
+    apt/yum tasks install the latest available package, or just ensure
+    that the package is present. The default action is to ensure that
+    the latest package is present. The action taken may be changed to
+    only ensure that the package is present by setting
+    ``rally_package_state`` to ``present``.
+upgrade:
+  - The os_rally role always checks whether the latest package is
+    installed when executed. If a deployer wishes to change the check to
+    only validate the presence of the package, the option
+    ``rally_package_state`` should be set to ``present``.

tasks/install-apt.yml

@@ -29,7 +29,7 @@
 - name: Install apt packages
   apt:
     pkg: "{{ item }}"
-    state: latest
+    state: "{{ rally_package_state }}"
   register: install_packages
   until: install_packages|success
   retries: 5