There are two APIs for checking the repair status and they behave
differently in case the id is not found.
```
{"host": "192.168.100.11:10001", "method": "GET", "uri":
"/storage_service/repair_async/system_auth?id=999", "duration": "1ms",
"status": 400, "bytes": 49, "dump": "HTTP/1.1 400 Bad
Request\r\nContent-Length: 49\r\nContent-Type: application/json\r\nDate:
Wed, 03 Nov 2021 10:49:33 GMT\r\nServer: Seastar
httpd\r\n\r\n{\"message\": \"unknown repair id 999\", \"code\": 400}"}
{"host": "192.168.100.11:10001", "method": "GET", "uri":
"/storage_service/repair_status?id=999&timeout=1", "duration": "0ms",
"status": 500, "bytes": 49, "dump": "HTTP/1.1 500 Internal Server
Error\r\nContent-Length: 49\r\nContent-Type: application/json\r\nDate:
Wed, 03 Nov 2021 10:49:33 GMT\r\nServer: Seastar
httpd\r\n\r\n{\"message\": \"unknown repair id 999\", \"code\": 500}"}
```
The correct status code is 400 as this is a parameter error and should
not be retried.
Returning status code 500 makes smarter http clients retry the request
in hopes of server recovering.
After this patch:
curl -X PGET
'http://127.0.0.1:10000/storage_service/repair_async/system_auth?id=9999'
{"message": "unknown repair id 9999", "code": 400}
curl -X GET
'http://127.0.0.1:10000/storage_service/repair_status?id=9999'
{"message": "unknown repair id 9999", "code": 400}
Fixes#9576Closes#9578
f5f5714aa6