packages: Fix service start on first boot

The *install-packages.service* unit has to be enabled, and the condition
checking for `/etc/ignition/packages.installed` was inverted.
Sending standard output to the console as well as the journal allows
watching progress.

install-packages.service

@@ -1,17 +1,19 @@
 # vim: set ft=systemd :
 [Unit]
-Description=Install collectd
+Description=Install additional packages
 After=network-online.target
 Wants=network-online.target
 Before=zincati.service
+Before=systemd-user-sessions.service
 ConditionPathExists=/etc/ignition/packages.d
-ConditionPathExists=/etc/ignition/packages.installed
+ConditionPathExists=!/etc/ignition/packages.installed
 
 [Service]
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=/bin/sh /etc/ignition/install-packages.sh
 ExecStartPost=/bin/touch /etc/ignition/packages.installed
+StandardOutput=journal+console
 
 [Install]
 WantedBy=multi-user.target

packages.yaml

@@ -14,3 +14,8 @@ storage:
     mode: 0644
     contents:
       local: install-packages.service
+
+systemd:
+  units:
+  - name: install-packages.service
+    enabled: true