Set higher priority for COPR repo

This patch sets the priority for the COPR repository on CentOS 7
(which we use to install LXC) to a higher priority than the default.
This ensures we always get our LXC packages from the COPR repo.

Change-Id: I07d127cb5fba8f4e30633da88eaecf9228eb350a

releasenotes/notes/copr-repo-priority-60b3603b0c1ff2f7.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    The COPR repository for installing LXC on CentOS 7 is now set to a higher
+    priority than the default to ensure that LXC packages always come from the
+    COPR repository.

tasks/lxc_install_yum.yml

@@ -22,7 +22,24 @@
     gpgcheck: yes
     gpgkey: "{{ lxc_centos_package_key }}"
     repo_gpgcheck: no
+    priority: 50
     state: present
+  register: copr_repository_deploy
+
+# NOTE: Existing CentOS environments may not have the COPR repo priority set
+#       higher than the default. The following task ensures that existing
+#       deployments have their priority adjusted for the COPR repository.
+# TODO(mhayden): The ini_file module is required here since the yum_repository
+#                module can only do add/remove operations, not edits.
+#                Ansible bug: https://github.com/ansible/ansible/issues/22362
+- name: Ensure COPR repository priority is set
+  ini_file:
+    dest: /etc/yum.repos.d/thm-lxc2.0.repo
+    section: thm-lxc2.0
+    option: priority
+    value: 50
+  when:
+    - not copr_repository_deploy | changed
 
 - name: Add GPG key for COPR LXC repo
   rpm_key: