Potential database connection leak

[0xyjk]

database rows does not closed

• https://github.com/0xPolygonHermez/zkevm-node/blob/develop/pool/pgpoolstorage/pgpoolstorage.go#L308

correct usage:

func queryRows() ([]A, error) {
    rows, err := db.Query("SELECT ....)
    if err != nil {
        return nil, err
    }
    defer rows.Close()

    var as []A

    for rows.Next() {
        var a A
        if err := rows.Scan(....); err != nil {
            return nil, err
        }
        as= append(as, a)
    }
    if err = rows.Err(); err != nil {
        return nil, err
    }
    return as, nil
}

should check rows.Err() for all query

• https://github.com/0xPolygonHermez/zkevm-node/blob/develop/pool/pgpoolstorage/pgpoolstorage.go#L204