consensus: don't wait for wal if conS not running

consensus/state.go

@@ -319,7 +319,7 @@ func (cs *ConsensusState) startRoutines(maxSteps int) {
 
 func (cs *ConsensusState) OnStop() {
 	cs.QuitService.OnStop()
-	if cs.wal != nil {
+	if cs.wal != nil && cs.IsRunning() {
 		cs.wal.Wait()
 	}
 }

consensus/wal.go

@@ -80,7 +80,7 @@ func (wal *WAL) Save(msg ConsensusLogMessageInterface) {
 	}
 }
 
-// Must not be called concurrently.
+// Must not be called concurrently with a write.
 func (wal *WAL) Close() {
 	if wal != nil {
 		wal.fp.Close()