[#274] wc: Make wait groups work more explicit

Do not run routine that calls `wg.Done()` inside, it is hard to read.

Signed-off-by: Pavel Karpy <p.karpy@yadro.com>

pkg/local_object_storage/writecache/flush.go

@@ -41,7 +41,10 @@ func (c *cache) runFlushLoop() {
 	}
 
 	c.wg.Add(1)
-	go c.flushBigObjects(context.TODO())
+	go func() {
+		c.flushBigObjects(context.TODO())
+		c.wg.Done()
+	}()
 
 	c.wg.Add(1)
 	go func() {
@@ -146,8 +149,6 @@ func (c *cache) flushDB() {
 }
 
 func (c *cache) flushBigObjects(ctx context.Context) {
-	defer c.wg.Done()
-
 	tick := time.NewTicker(defaultFlushInterval * 10)
 	for {
 		select {