Add simple playbook task for upgrading servers

We want to treat our servers as cattle; hopefully when this is fleshed out a bit more, it can accomplish the job without too many casualties.

playbooks/tasks/include/upgrade-server.yml

@@ -14,14 +14,14 @@
 
 - name: check for running builds
   block:
-    - name: list systemd-nspawn processes
-      command: pgrep -x systemd-nspawn
-      register: pgrep_systemd_nspawn
+    - name: list build-related processes
+      command: pgrep -x 'mkarchroot|makechrootpkg|systemd-nspawn'
+      register: pgrep
       ignore_errors: true
 
     - name: abort reboot with running builds
       meta: end_host
-      when: pgrep_systemd_nspawn is succeeded
+      when: pgrep is succeeded
   when: "'buildservers' in group_names"
 
 - name: gemini pre-reboot checks