Start no account's manager to look at its units (hq issue 764)

Every 15 s the failed-units look read the own manager of every account
the declaration creates, and reading one is a login that starts it: six
module accounts' managers on the control node started and stopped all
day, most of its journal. A look only reads (ADR 0240 rule 6) and never
asks an account's manager (ADR 0177).

An account's manager is read now only when the declaration places a
user-scoped unit in it, and only after the machine's own manager says
user@<uid>.service is active, as the apply asks before it. A manager not
running is said away in the units statement, with no failed units; in
liveness its units read unknown with the apply's words, never down. The
operator's account on a desktop is still read while logged in, since a
module places a user unit there (issue 315's Razer daemon stays said).

cmd/mesh-host/main.go

@@ -1130,7 +1130,7 @@ func runLink(ctx context.Context, opts options) error {
 	// The one liveness judge on this machine (novox/hq ADR 0240), made before anything applies: every
 	// report this host makes carries what it says.
 	if j, err := liveness.Open(filepath.Join(filepath.Dir(opts.state), liveness.FileName),
-		&liveness.Exec{Run: apply.ExecRunner}); j != nil {
+		&liveness.Exec{Run: apply.ExecRunner, System: builtFor}); j != nil {
 		if err != nil {
 			say(err.Error())
 		}
@@ -1794,7 +1794,8 @@ func withUnits(h *link.Health, us *units.Statement) *link.Health {
 	if us == nil || us.State == "" {
 		return h
 	}
-	h.Units = &link.UnitsHealth{State: us.State, Failed: []link.FailedUnit{}, Unread: us.Unread}
+	h.Units = &link.UnitsHealth{State: us.State, Failed: []link.FailedUnit{}, Unread: us.Unread,
+		Away: us.Away}
 	for _, f := range us.Failed {
 		if f.Module == "" {
 			h.Units.Failed = append(h.Units.Failed, link.FailedUnit{Unit: f.Unit, Scope: f.Scope, Load: f.Load,