Fix obd goroutine leak

[klauspost]

Description

The gouroutine collecting transfer stats never exits. Add missing channel close.

How to test this PR?

Run obd test. Observe leaked goroutines.

Types of changes

• Cleanup

[minio-trusted]

Mint Automation

Test	Result
mint-large-bucket.sh	✔️
mint-fs.sh	✔️
mint-gateway-s3.sh	✔️
mint-erasure.sh	✔️
mint-dist-erasure.sh	✔️
mint-zoned.sh	✔️
mint-gateway-nas.sh	✔️
mint-gateway-azure.sh	❌ more...

10504-8072776/mint-gateway-azure.sh.log:

Running with
SERVER_ENDPOINT:      minio-dev7.minio.io:32739
ACCESS_KEY:           minioazure
SECRET_KEY:           ***REDACTED***
ENABLE_HTTPS:         0
SERVER_REGION:        us-east-1
MINT_DATA_DIR:        /mint/data
MINT_MODE:            full
ENABLE_VIRTUAL_STYLE: 0

To get logs, run 'docker cp 21ce2b7d8510:/mint/log /tmp/mint-logs'

(1/15) Running aws-sdk-go tests ... done in 9 seconds
(2/15) Running aws-sdk-java tests ... done in 1 seconds
(3/15) Running aws-sdk-php tests ... done in 1 minutes and 46 seconds
(4/15) Running aws-sdk-ruby tests ... done in 20 seconds
(5/15) Running awscli tests ... done in 3 minutes and 2 seconds
(6/15) Running healthcheck tests ... done in 0 seconds
(7/15) Running mc tests ... done in 5 minutes and 51 seconds
(8/15) Running minio-dotnet tests ... done in 1 minutes and 39 seconds
(9/15) Running minio-go tests ... FAILED in 2 minutes and 24 seconds
{
  "args": {
    "bucketName": "minio-go-test-gtewi9iamw1jgeva",
    "objectName": "pmv36ftw2vr4z4qdk4ac0h5c1fnxie"
  },
  "duration": 730,
  "error": "EOF",
  "function": "GetObject(bucketName, objectName)",
  "message": "Error reading through readFull",
  "name": "minio-go: testGetObjectSeekEnd",
  "status": "FAIL"
}
(9/15) Running minio-java tests ... done in 10 minutes and 59 seconds
(10/15) Running minio-js tests ... done in 2 minutes and 46 seconds
(11/15) Running minio-py tests ... done in 18 minutes and 14 seconds
(12/15) Running s3cmd tests ... done in 2 minutes and 15 seconds
(13/15) Running s3select tests ... done in 1 minutes and 4 seconds
(14/15) Running security tests ... done in 0 seconds

Executed 14 out of 15 tests successfully.

Deleting image on docker hub
Deleting image locally
Error: No such image: minio/minio:10504-8072776

[kannappanr]

LGTM