pve-exporter: Install properly configuration and service

Related to T3462

Test Plan

$ bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details --to staging branly
...
*** Running octocatalog-diff on host branly.internal.softwareheritage.org
I, [2021-08-12T09:25:37.895070 #1045]  INFO -- : Catalogs compiled for branly.internal.softwareheritage.org
I, [2021-08-12T09:25:38.852846 #1045]  INFO -- : Diffs computed for branly.internal.softwareheritage.org
diff origin/production/branly.internal.softwareheritage.org current/branly.internal.softwareheritage.org
*******************************************
  File[/etc/pve-exporter] =>
   parameters =>
     ensure =>
      - present
      + directory
     notify =>
      + ["File[/etc/pve-exporter/pve-exporter.yml]"]
*******************************************
+ File[/etc/systemd/system/prometheus-pve-exporter.service] =>
   parameters =>
      "ensure": "file"
      "group": "root"
      "mode": "0444"
      "notify": "Class[Systemd::Systemctl::Daemon_reload]"
      "owner": "root"
      "show_diff": true
      "content": >>>
[Unit]
Description=Proxmox VE Prometheus Exporter
After=network.target
Wants=network.target
[Service]
Restart=on-failure
WorkingDirectory=/tmp
ExecStart=/usr/bin/pve_exporter /etc/pve-exporter/pve-exporter.yml
[Install]
WantedBy=multi-user.target
<<<
*******************************************
- File[prometheus-pve-exporter.service]
*******************************************
+ Service[prometheus-pve-exporter.service] =>
   parameters =>
      "enable": true
      "ensure": "running"
*******************************************
+ Systemd::Unit_file[prometheus-pve-exporter.service] =>
   parameters =>
      "ensure": "present"
      "group": "root"
      "mode": "0444"
      "notify": ["Service[prometheus-pve-exporter.service]"]
      "owner": "root"
      "path": "/etc/systemd/system"
      "show_diff": true
      "content": >>>
[Unit]
Description=Proxmox VE Prometheus Exporter
After=network.target
Wants=network.target
[Service]
Restart=on-failure
WorkingDirectory=/tmp
ExecStart=/usr/bin/pve_exporter /etc/pve-exporter/pve-exporter.yml
[Install]
WantedBy=multi-user.target
<<<
*******************************************
*** End octocatalog-diff on branly.internal.softwareheritage.org

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Migrated from D6078 (view on Phabricator)