Allow deployers to configure yum fastestmirror

This patch uses the new ``openstack_hosts_enable_yum_fastestmirror``
variable to determine whether yum's fastestmirror plugin should be
enabled.

Depends-On: I8b2a1db084ab47962dbef8c6b037836f44b4ed46
Change-Id: Id340ac48a551081031b14804d376e6e5d744fa0d

defaults/main.yml

@@ -147,3 +147,6 @@ opensuse_obs_cloud_repo_url: "{{ opensuse_mirror_obs }}/repositories/Cloud:/Open
 
 # Keep a history of systemd journals on disk after reboots
 openstack_host_keep_journals: yes
+
+# Enable/Disable the yum fastestmirror plugin
+openstack_hosts_enable_yum_fastestmirror: yes

releasenotes/notes/fastestmirror-configurable-08e075f8602164e5.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Deployers of CentOS 7 environments can use the
+    ``openstack_hosts_enable_yum_fastestmirror`` variable to enable or disable
+    yum's fastestmirror plugin. The default setting of ``yes`` ensures that
+    fastestmirror is enabled.

tasks/openstack_hosts_configure_yum.yml

@@ -13,6 +13,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Check to see if yum's fastestmirror plugin is present
+  stat:
+    path: /etc/yum/pluginconf.d/fastestmirror.conf
+  register: fastestmirror_plugin_check
+
+- name: Configure yum's fastestmirror plugin
+  ini_file:
+    path: /etc/yum/pluginconf.d/fastestmirror.conf
+    section: main
+    option: enabled
+    value: "{{ (openstack_hosts_enable_yum_fastestmirror | bool) | ternary('1', '0') }}"
+    no_extra_spaces: yes
+  when:
+    - fastestmirror_plugin_check.stat.exists
+
 - name: Disable requiretty for root sudo on centos
   template:
     dest: /etc/sudoers.d/openstack-ansible