After SFTP backup, the backup file and the iso must be deleted from the machine

Currently, the SFTP backup leaves huge archives on the machine that the
backup has been taken. This change adds a cleanup task to the
backup&restore role. Also, to perform an SFTP backup, it is needed that
the SSH fingerprint of the storage node is downloaded on the node.
Although this could be done by hand, this change automates also this
action.

As the directory structure is not the same in train as it is in more
advanced versions, this cherry pick is not completely clean, and some
rework needed to be done to put the code in the right place.

bz#1955495

Change-Id: I7b8df9cf8a56606f3db54f00af547378e4f4e472
(cherry picked from commit afe69e3dbf)

tripleo_ansible/roles/backup-and-restore/backup/tasks/main.yml

@@ -45,3 +45,14 @@
     var: tripleo_backup_and_restore_rear_output
   tags:
     - bar_create_recover_image
+
+- name: Clean old backups
+  shell: |
+    set -o pipefail
+    rm -rf /tmp/rear.* || true
+    rm -rf /var/lib/rear/output/*
+  failed_when: false
+  args:
+    warn: false
+  tags:
+    - bar_create_recover_image

tripleo_ansible/roles/backup-and-restore/setup_rear/tasks/main.yml

@@ -109,3 +109,36 @@
     backup: true
   tags:
     - bar_setup_rear
+
+- name: Load rear config
+  become: true
+  slurp:
+    src: /etc/rear/local.conf
+  register: rear_config
+  tags:
+    - bar_setup_rear
+
+- name: Extract OUTPUT_URL from rear config
+  set_fact:
+    output_url: "{{ rear_config.content | b64decode | regex_findall('OUTPUT_URL=(.+)') | first }}"
+  tags:
+    - bar_setup_rear
+
+- name: Check if this is a SFTP backup
+  set_fact:
+    sftp_backup: "{{ output_url is search ('sftp://') }}"
+  tags:
+    - bar_setup_rear
+
+- name: Extract the SFTP hostname
+  set_fact:
+    sftp_host: "{{ output_url | regex_search('(?<=@)(.*?)(?=/)') }}"
+  when: sftp_backup
+  tags:
+    - bar_setup_rear
+
+- name: Retrieve host ssh fingerprint
+  shell: "ssh-keyscan -H {{ sftp_host }} >> ~/.ssh/known_hosts"
+  when: sftp_backup
+  tags:
+    - bar_setup_rear