__systemd_unit: fix crash when transitioning to state=absent

This type tried to disable an unit after it has removed it, which
failed. Now the removal happens in gencode-remote, after the unit has
been stopped and disabled.

cdist/conf/type/__systemd_unit/gencode-remote

@@ -25,6 +25,8 @@ current_enablement_state=$(cat "${__object}/explorer/enablement-state")
 if [ "${state}" = "absent" ]; then
     if [ ! -z "${current_enablement_state}" ]; then
         echo "systemctl --now disable ${name}"
+        echo "rm -f /etc/systemd/system/${name}"
+        echo "systemctl daemon-reload"
     fi
 
     exit 0

cdist/conf/type/__systemd_unit/manifest

@@ -30,7 +30,9 @@ name="${__object_id}"
 source=$(cat "${__object}/parameter/source")
 state=$(cat "${__object}/parameter/state")
 
-if [ -z "${source}" ] && [ "${state}" != "absent" ]; then
+# The unit must be disabled before removing its unit file. The unit file is
+# therefore removed by gencode-remote of this type, not here.
+if [ -z "${source}" ] || [ "${state}" = "absent" ]; then
     exit 0
 fi