[#725] writecache: Fix metric values

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/writecache/writecachebbolt/storage.go

@@ -73,7 +73,7 @@ func (c *cache) deleteFromDB(key string) {
 	err := c.db.Batch(func(tx *bbolt.Tx) error {
 		b := tx.Bucket(defaultBucket)
 		key := []byte(key)
-		recordDeleted = !recordDeleted && b.Get(key) != nil
+		recordDeleted = b.Get(key) != nil
 		return b.Delete(key)
 	})
 
@@ -122,6 +122,7 @@ func (c *cache) deleteFromDisk(ctx context.Context, keys []string) []string {
 				storagelog.OpField("fstree DELETE"),
 			)
 			c.metrics.Evict(writecache.StorageTypeFSTree)
+			// counter changed by fstree
 			c.estimateCacheSize()
 		}
 	}