core: fix deadlock in headers list init

This probably is a problem since adc880d323,
because AddHeaders() uses headersOp channel and its reader is only ran in
Run().

pkg/core/blockchain.go

@@ -148,8 +148,11 @@ func (bc *Blockchain) init() error {
 		}
 
 		headerSliceReverse(headers)
-		if err := bc.AddHeaders(headers...); err != nil {
+		for _, h := range headers {
-			return err
+			if !h.Verify() {
+				return fmt.Errorf("bad header %d/%s in the storage", h.Index, h.Hash())
+			}
+			bc.headerList.Add(h.Hash())
 		}
 	}