Too much time wait the client to resume file download if the seeders goes online

### Step 1: Please describe your environment

* ZeroNet version: 0.7.1 (rev4445)
* Operating system: Windows 10
* Web browser: Firefox 72.02
* Tor status: not always
* Opened port: no
* Special configuration:

Used 2 different wifi netwotks with 2 different internet provider. 150KB/s upload speed. 3GB of total files in cc 500 MB/ file.1 week period and the computers serval times goes off and on. And not all 2 PC always active at the same time.

### Step 2: Describe the problem:

Too much time wait the client to resume file download if the seeders goes online. Without the user interaction using the refresh button and shows example 2000 file left. Too much time passes when the seeder goes online and the client start to download the files.This largely increases the time it takes for the files to be fully downloaded. 5piece cc 500-600MB total 3 GB file about 1 week downloaded. Which is a lot of time.

#### Steps to reproduce:

1. Use 2 PC with 2 different internet provider what restarted, and behave like any other PC in the internet.

#### Observed Results:

When the seeder goes online too much time passes when the client start refresh the current page and download the files. Without the auto refreshing the page files will not downloading.About hours the client does not download the files even if the seeder are goes online.

#### Expected Results:

Better detect it if the another client are online. About 1 week from 3GB of total files using 150KB/s upload speed it's a lot of time. And there was too much time to the 2 PC was the same time online and the client can download the file, but it didn't.

报告中没有指出源文件、测试或入口点。首先复现两台 PC 的下载场景，并跟踪客户端如何发现 seeder 返回；完成的标准是：无需刷新页面，下载即可自动恢复，并且延迟得到降低。

由索引模型根据 Issue 内容生成。