BaR: Keep /etc/exports content

Currently the backup and restore role when is installing the nfs server,
the role uses a template to generate the /etc/exports file. This means
that if there already an nfs server installed with its configuration
the /etc/exports will be overwritten.

This patch keeps the configuration of the /etc/exports and appends
the "new" part.

Closes-Bug: #1897503
Closes BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1878480

Change-Id: I0b943047be06153504fabe895711cce789621ac5

tripleo_ansible/roles/backup_and_restore/tasks/setup_nfs.yml

@@ -85,14 +85,17 @@
   tags:
     - bar_setup_nfs_server
 
-- name: Generate NFS exports table in the server
-  become: true
-  template:
-    src: exports.j2
-    dest: /etc/exports
-    owner: root
-    group: root
-    mode: '0644'
+- name: Get the lines
+  set_fact:
+    bar_exportfs_lines: "{% for net in tripleo_backup_and_restore_nfs_clients_nets %}\
+      {{ tripleo_backup_and_restore_nfs_storage_folder }} {{ net }}(rw,sync,no_root_squash,no_subtree_check)\n{% endfor %}"
+  tags:
+    - bar_setup_nfs_server
+
+- name: NFS
+  blockinfile:
+    path: /etc/exports
+    block: "{{bar_exportfs_lines}}"
     backup: true
   tags:
     - bar_setup_nfs_server

tripleo_ansible/roles/backup_and_restore/templates/exports.j2

@@ -1,8 +0,0 @@
-# This configuration file is generated automatically
-# by the backup_and_restore role part of TripleO
-# Ansible. No not edit this file, all changes
-# will be lost. Refer to the following URL for
-# more information and implementation details:
-# https://opendev.org/openstack/tripleo-ansible
-
-{{ tripleo_backup_and_restore_nfs_storage_folder }} {% for net in tripleo_backup_and_restore_nfs_clients_nets %}{{ net }}(rw,sync,no_root_squash,no_subtree_check) {% endfor %}