cmd/mbf: cancel remote cure

This exposes the new fine-grained cancel API in cmd/mbf.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/mbf/daemon_test.go

@@ -109,6 +109,11 @@ func TestDaemon(t *testing.T) {
 	if err != nil {
 		t.Fatalf("cureRemote: error = %v", err)
 	}
+
+	if err = cancelRemote(ctx, &addr, pkg.NewFile("nonexistent", nil)); err != nil {
+		t.Fatalf("cancelRemote: error = %v", err)
+	}
+
 	cancel()
 	<-done
 
@@ -118,6 +123,7 @@ func TestDaemon(t *testing.T) {
 	}
 
 	const wantLog = `daemon: fulfilled artifact fiZf-ZY_Yq6qxJNrHbMiIPYCsGkUiKCRsZrcSELXTqZWtCnESlHmzV5ThhWWGGYG
+daemon: attempted to cancel invalid artifact kQm9fmnCmXST1-MMmxzcau2oKZCXXrlZydo4PkeV5hO_2PKfeC8t98hrbV_ZZx_j
 `
 	if gotLog := buf.String(); gotLog != wantLog {
 		t.Errorf("serve: logged\n%s\nwant\n%s", gotLog, wantLog)