Remove percona repo if not used

If the ``use_percona_upstream`` value is changed from True to False,
don't remove the existing repository. This is also the source of a bug
in Mitaka: We were installing the repo by default and installed the
percona-xtrabackup tool with a deb file. If another playbook/role
installed percona-xtrabackup, it would override (and probably upgrade)
the deb installed version, which is undesired.

Combined backport of:
- https://review.openstack.org/#/c/417362/
- https://review.openstack.org/#/c/417776/
- https://review.openstack.org/#/c/416234/

Change-Id: Ibb2f01e6b61774a2517feb5baf4a5452b7f68a84
Closes-Bug: 1653947
Signed-off-by: Jean-Philippe Evrard <jean-philippe.evrard@rackspace.co.uk>

releasenotes/notes/apt-source-filenamed-9f83d18619debf26.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - The filename of the apt source can now be defined
+    with the variable ``filename`` inside the dicts
+    ``galera_repo`` and
+    ``galera_percona_xtrabackup_repo``.

releasenotes/notes/make-sure-the-repo-is-removed-if-not-used-36670d0a276192f1.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - The percona repository stayed in placed even after
+    a change of the variable ``use_percona_upstream``.
+    From now on, the percona repository will not be
+    present unless the deployer decides to
+    ``use_percona_upstream``. This also fixes a bug
+    of the presence of this apt repository after an
+    upgdrade from Mitaka.

tasks/galera_install_apt.yml

@@ -75,28 +75,25 @@
 
 - name: Add galera repo
   apt_repository:
-    repo: "{{ item.repo }}"
-    state: "{{ item.state }}"
+    repo: "{{ galera_repo.repo }}"
+    filename: "{{ galera_repo.filename | default(omit) }}"
+    state: "{{ galera_repo.state }}"
   register: add_repos
   until: add_repos|success
   retries: 5
   delay: 2
-  with_items:
-    - "{{ galera_repo }}"
   tags:
     - galera-repos
 
 - name: Add percona repo
   apt_repository:
-    repo: "{{ item.repo }}"
-    state: "{{ item.state }}"
+    repo: "{{ galera_percona_xtrabackup_repo.repo }}"
+    filename: "{{ galera_percona_xtrabackup_repo.filename | default(omit) }}"
+    state: "{{ use_percona_upstream | bool | ternary('present','absent') }}"
   register: add_repos
   until: add_repos|success
   retries: 5
   delay: 2
-  with_items:
-    - "{{ galera_percona_xtrabackup_repo }}"
-  when: use_percona_upstream | bool
   tags:
     - percona-repos