Raise a failed unit, the module's and the machine's (hq issue 315)

A module's failed unit now arrives among its resources and raises the
module's own condition, named by the unit. The machine's own failed
units, which no module places, are one warning for the machine listing
them, cleared when none is listed. Nothing a send moved is among them,
so the gate never holds a send on that finding. The statement's units
are kept with the machine's health (migration 0080) and node show says
them.

cmd/mesh-controller/gate.go

@@ -348,6 +348,10 @@ func aboutTheMachine(machine string, moved []string, since time.Time, f gateFact
 			}
 		case coreBehind:
 			// Not what the send moved: said nowhere against it.
+		case c.Kind == kindMachineUnits:
+			// **The machine's own failed units** (issue 315): no module places any of them, so nothing a
+			// send moved is among them — a module's failed unit is that module's own condition. Said
+			// nowhere against the send.
 		case c.Kind == kindNetworkRewritten || c.Kind == kindNetworkUnreachable && c.Subject.ID != machine:
 			// **Shown to be somebody else's** (ADR 0241): another program rewrote the resolver file the send
 			// did not move, or the machine cannot reach another that is down. Nothing the send did; the