If there is a BR backup --s3.endpoint command is brought /, the backup will fail

[jacktd9]

Please answer these questions before submitting your issue. Thanks!

The s3 compatible storage is Minio S3 or HCP S3.

Failed command
Error info failed to put object Request ID: None Body

export AWS_ACCESS_KEY_ID=${AccessKey}
export AWS_SECRET_ACCESS_KEY=${SecretKey}
./br backup full --pd http://192.168.1.1:2379 --storage "s3://tidb/br20210528_full/" --send-credentials-to-tikv=true --s3.endpoint "http://192.168.1.1:9000/" 
Detail BR log in /tmp/br.log.2021-05-31T23.58.09+0800 
Full backup <............................................................................................................................................................................> 0.00%
Error: msg:"Io(Custom { kind: Other, error: \"failed to put object Request ID: None Body: <?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?>\\n<Error><Code>XMinioUnknownAPIRequest</Code><Message>Unknown API request at //tidb/br20210528_full/7_58213_1592_91da88fe2a00123564e3b657c69a8e290a2e3c9d3c87227a7504138f5df0a06f_1622476689590_write.sst</Message><Resource>//tidb/br20210528_full/7_58213_1592_91da88fe2a00123564e3b657c69a8e290a2e3c9d3c87227a7504138f5df0a06f_1622476689590_write.sst</Resource><RequestId></RequestId><HostId>83dbe45f-2508-4af3-9cf1-30f77f762c61</HostId></Error>\" })" : [BR:KV:ErrKVUnknown]unknown tikv error

Successful command

export AWS_ACCESS_KEY_ID=${AccessKey}
export AWS_SECRET_ACCESS_KEY=${SecretKey}
./br backup full --pd http://192.168.1.1:2379 --storage "s3://tidb/br20210528_full/" --send-credentials-to-tikv=true --s3.endpoint "http://192.168.1.1:9000" 
Detail BR log in /tmp/br.log.2021-05-31T23.59.10+0800 
Full backup <-------------------------..................................................................................................................................................> 14.33%

different
If the command is brought / backup will fail

Successful 
--s3.endpoint "http://192.168.1.1:9000" 
Failed 
--s3.endpoint "http://192.168.1.1:9000/" 

1. What did you do?
   Run backup

2. What did you expect to see?
   Backup success

3. What did you see instead?
   Backup fail

4. What version of BR and TiDB/TiKV/PD are you using?
   TiDB cluster v4.0.10
   BR v4.0.10 & v4.0.12

[kennytm]

duplicate of #992