import task should retry on GCS error `server sent GOAWAY`

[joechenrh]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

When importing data from GCS, sometimes we may encounter errors like http2: server sent GOAWAY and closed the connection; LastStreamID=XXX, ErrCode=NO_ERROR, debug="server_shutting_down", and this error can be resolved through retry.

But currently, this error is not included in the retry error list.

2. What did you expect to see? (Required)

Subtask should retry after meeting this error.

3. What did you see instead (Required)

Subtask failed.

4. What is your TiDB version? (Required)

master

[joechenrh]

/severity moderate