rebuilderd_worker: start removing stale chroots

On some build failures, or perhaps when rebooting the boxes while a
build is ongoing, repro chroots can be left behind taking up space.

Add a service with a daily timer to remove week old chroots.

roles/rebuilderd_worker/files/clean-repro

+#!/bin/bash -e
+
+find /var/lib/repro -maxdepth 1 -name '*?_?*' -mtime +6 -exec rm -rf {} +

roles/rebuilderd_worker/files/clean-repro.service

+[Unit]
+Description=Clean up stale repro chroots
+ConditionPathExists=/var/lib/repro
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/bin/clean-repro
+Nice=19
+IOSchedulingClass=best-effort
+IOSchedulingPriority=7

roles/rebuilderd_worker/files/clean-repro.timer

+[Unit]
+Description=Daily repro cleanup
+
+[Timer]
+OnCalendar=daily
+RandomizedDelaySec=12h
+Persistent=true
+
+[Install]
+WantedBy=timers.target

roles/rebuilderd_worker/handlers/main.yml

+---
+
+- name: daemon reload
+  systemd:
+    daemon-reload: true

roles/rebuilderd_worker/tasks/main.yml

@@ -13,3 +13,17 @@
 - name: enable and start rebuilderd-worker@{{ item }}
   systemd: name=rebuilderd-worker@{{ item }} enabled=yes state=started
   with_items: '{{ rebuilderd_workers }}'
+
+- name: install cleanup script
+  copy: src=clean-repro dest=/usr/local/bin/clean-repro owner=root group=root mode=0755
+
+- name: install cleanup units
+  copy: src={{ item }} dest=/etc/systemd/system/{{ item }} owner=root group=root mode=0644
+  loop:
+    - clean-repro.timer
+    - clean-repro.service
+  notify:
+    - daemon reload
+
+- name: start and enable cleanup timer
+  service: name=clean-repro.timer enabled=yes state=started