Allow override of the repo filename

Apt cannot have 2 mirrors with the same content in 2 different files.
If a deployer has an apt mirror with mariadb (and others), the deployer
still need to add a repository, but will also need to define the
filename used, in order to avoid clashes.

This commit makes possible to decide the filename for the repo.

Change-Id: I047bdaf58a4057a96103f6d56c2f811886b1b625
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``.

tasks/galera_install_apt.yml

@@ -73,7 +73,7 @@
 - name: Add galera repo
   apt_repository:
     repo: "{{ galera_repo.repo }}"
-    filename: MariaDB
+    filename: "{{ galera_repo.filename }}"
     state: "{{ galera_repo.state }}"
   register: add_repos
   until: add_repos|success
@@ -85,7 +85,7 @@
 - name: Add percona repo
   apt_repository:
     repo: "{{ galera_percona_xtrabackup_repo.repo }}"
-    filename: Percona
+    filename: "{{ galera_percona_xtrabackup_repo.filename }}"
     state: "{{ galera_percona_xtrabackup_repo.state }}"
   register: add_repos
   until: add_repos|success

vars/ubuntu-16.04.yml

@@ -91,10 +91,12 @@ galera_percona_xtrabackup_repo_url: "http://repo.percona.com/apt"
 galera_percona_xtrabackup_repo:
   repo: "deb {{ galera_percona_xtrabackup_repo_url }} {{ ansible_distribution_release }} main"
   state: "present"
+  filename: "Percona"
 
 _galera_repo_url: "http://mirror.rackspace.com/mariadb/repo/10.1/ubuntu"
 galera_repo:
   repo: "deb {{ galera_repo_url }} {{ ansible_distribution_release }} main"
   state: "present"
+  filename: "MariaDB"
 
 use_percona_upstream: no