[#314] wc: Do not lose small objects on disk errors

Do return error if an object could not been stored on WC's disk.

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

pkg/local_object_storage/writecache/put.go

@@ -78,7 +78,7 @@ func (c *Cache) putSmall(obj objectInfo) error {
 		)
 		c.objCounters.IncDB()
 	}
-	return nil
+	return err
 }
 
 // putBig writes object to FSTree and pushes it to the flush workers queue.