TiFlash may fail to start if fstat got stuck on NFS devices

Enhancement

Will call fn_server_info at beginning

fn disk_hardware_info(collector: &mut Vec<ServerInfoItem>) {
    let mut system = SYS_INFO.lock().unwrap();
    system.refresh_disks_list();
    system.refresh_disks();
    let disks = system.get_disks();
    for disk in disks {
        let file_sys = std::str::from_utf8(disk.get_file_system()).unwrap_or("unknown");
...

Which is

fn new_disk(name: &OsStr, mount_point: &Path, file_system: &[u8]) -> Option<Disk> {
    let mount_point_cpath = utils::to_cpath(mount_point);
    let type_ = find_type_for_name(name);
    let mut total = 0;
    let mut available = 0;
    unsafe {
        let mut stat: statvfs = mem::zeroed();
        if statvfs(mount_point_cpath.as_ptr() as *const _, &mut stat) == 0 {
            total = cast!(stat.f_bsize) * cast!(stat.f_blocks);
            available = cast!(stat.f_bsize) * cast!(stat.f_bavail);
        }
    }
...

Start by tracing the startup path to fn_server_info and disk_hardware_info, then inspect new_disk and its statvfs call. Reproduce or reason about startup with an NFS mount that blocks filesystem statistics; done means TiFlash can start without hanging on that device.