[#1667] shard: Drop shard pool

After adding an ops limiter, shard's `put` pool is redundant.

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

pkg/local_object_storage/engine/control.go

@@ -153,16 +153,10 @@ func (e *StorageEngine) Close(ctx context.Context) error {
 }
 
 // closes all shards. Never returns an error, shard errors are logged.
-func (e *StorageEngine) close(ctx context.Context, releasePools bool) error {
+func (e *StorageEngine) close(ctx context.Context) error {
 	e.mtx.RLock()
 	defer e.mtx.RUnlock()
 
-	if releasePools {
-		for _, p := range e.shardPools {
-			p.Release()
-		}
-	}
-
 	for id, sh := range e.shards {
 		if err := sh.Close(ctx); err != nil {
 			e.log.Debug(ctx, logs.EngineCouldNotCloseShard,
@@ -213,7 +207,7 @@ func (e *StorageEngine) setBlockExecErr(ctx context.Context, err error) error {
 			return e.open(ctx)
 		}
 	} else if prevErr == nil { // ok -> block
-		return e.close(ctx, errors.Is(err, errClosed))
+		return e.close(ctx)
 	}
 
 	// otherwise do nothing