contractcourt: fix concurrent access to launched

contractcourt/breach_resolver.go

@@ -130,13 +130,13 @@ var _ ContractResolver = (*breachResolver)(nil)
 //
 // TODO(yy): implement it once the outputs are offered to the sweeper.
 func (b *breachResolver) Launch() error {
-	if b.launched {
+	if b.isLaunched() {
 		b.log.Tracef("already launched")
 		return nil
 	}
 
 	b.log.Debugf("launching resolver...")
-	b.launched = true
+	b.markLaunched()
 
 	return nil
 }