Remove what an earlier delivery of a check left before raising its store again

An ask redelivered after the build agent stopped mid-check (the rollout it was checking updated it)
found its own throwaway store under its name, and the check said it could not run (mesh-controller#105,
build-1791331512096605198).

internal/builder/check.go

@@ -298,6 +298,13 @@ func Check(ctx context.Context, run Runner, spec CheckSpec, workspace, registry
 	say("check", "the facts of %s (%s): %d machine(s), the bus at %s, the store at %s", f.Taken.Format(time.RFC3339),
 		short(strings.TrimPrefix(digest, "sha256:")), len(f.Machines), f.Versions.Bus, f.Versions.Store)
 
+	// **What an earlier delivery of this same ask left is removed first** (novox/hq issue 285): an ask is
+	// redelivered when the holder that took it stopped mid-check — the build agent itself updated by the
+	// rollout it is checking — and its containers, named by the ask's id, are still there. Raising the
+	// store again under that name was refused, and the check said it could not run.
+	if n, err := RemoveContainersOf(ctx, run, spec.ID); err == nil && n > 0 {
+		say("check", "removed %d throwaway container(s) an earlier delivery of this check left", n)
+	}
 	// The throwaway store and bus, of the versions the mesh runs, removed whatever happens.
 	defer func() {
 		removing, done := context.WithTimeout(context.Background(), time.Minute)