Add LDAP DNS SRV record lookup support

[donatello]

Description

The main change is in the minio/pkg lib, this change updates docs and adds configuration option.

Needs minio/pkg#52

Motivation and Context

DNS SRV records are used for LDAP high-availability - https://ldap.com/dns-srv-records-for-ldap/

How to test this PR?

Test setup would need a configured DNS SRV record - this change is not end to end tested. However, it is possible to ensure that DNS SRV querying is working by picking a public DNS SRV record (e.g. _ldap._tcp.google.com ) - obviously cannot login with that, you can get a credentials invalid error.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[minio-trusted]

Mint Automation

Test	Result
mint-large-bucket.sh	✔️
mint-fs.sh	✔️
mint-erasure.sh	✔️
mint-dist-erasure.sh	✔️
mint-compress-encrypt-dist-erasure.sh	✔️
mint-pools.sh	❌ more...

16201-7765bee/mint-pools.sh.log:

Running with
SERVER_ENDPOINT:      15.15.15.6:31685
ACCESS_KEY:           minio
SECRET_KEY:           ***REDACTED***
ENABLE_HTTPS:         0
SERVER_REGION:        us-east-1
MINT_DATA_DIR:        /mint/data
MINT_MODE:            full
ENABLE_VIRTUAL_STYLE: 0
RUN_ON_FAIL:          0

To get logs, run 'docker cp 071110e910aa:/mint/log /tmp/mint-logs'

(1/14) Running aws-sdk-go tests ... done in 2 seconds
(2/14) Running aws-sdk-java tests ... done in 1 seconds
(3/14) Running aws-sdk-php tests ... done in 43 seconds
(4/14) Running aws-sdk-ruby tests ... done in 7 seconds
(5/14) Running awscli tests ... FAILED in 17 seconds
{
  "name": "awscli",
  "duration": 11519,
  "function": "delete_bucket\n",
  "status": "FAIL",
  "error": "fatal error: An error occurred (InternalError) when calling the ListObjectsV2 operation (reached max retries: 4): We encountered an internal error, please try again.: cause(listPathRaw: 0 drives provided)remove_bucket failed: Unable to delete all objects in the bucket, bucket will not be deleted."
}
(5/14) Running healthcheck tests ... done in 0 seconds
(6/14) Running mc tests ... done in 54 seconds
(7/14) Running minio-go tests ... FAILED in 9 seconds
{
  "args": {
    "bucketName": "minio-go-test-bbhq4vv0o5clwya1",
    "region": "eu-west-1"
  },
  "duration": 4417,
  "error": "We encountered an internal error, please try again.: cause(listPathRaw: 0 drives provided)",
  "function": "MakeBucket(bucketName, region)",
  "message": "CleanupBucket failed while removing bucket recursively",
  "name": "minio-go: testMakeBucketRegionsV2",
  "status": "FAIL"
}
(7/14) Running minio-java tests ... done in 35 seconds
(8/14) Running minio-js tests ... FAILED in 11 seconds
{
  "name": "minio-js",
  "function": "\"after all\" hook in \"functional tests\"",
  "duration": 6,
  "status": "FAIL",
  "error": "S3Error: The bucket you tried to delete is not empty at Object.parseError (node_modules/minio/dist/main/xml-parsers.js:71:11) at /mint/run/core/minio-js/node_modules/minio/dist/main/transformers.js:166:22 at DestroyableTransform._flush (node_modules/minio/dist/main/transformers.js:90:10) at DestroyableTransform.prefinish (node_modules/readable-stream/lib/_stream_transform.js:129:10) at prefinish (node_modules/readable-stream/lib/_stream_writable.js:611:14) at finishMaybe (node_modules/readable-stream/lib/_stream_writable.js:620:5) at endWritable (node_modules/readable-stream/lib/_stream_writable.js:643:3) at DestroyableTransform.Writable.end (node_modules/readable-stream/lib/_stream_writable.js:571:22) at IncomingMessage.onend (internal/streams/readable.js:670:10) at endReadableNT (internal/streams/readable.js:1333:12) at processTicksAndRejections (internal/process/task_queues.js:82:21)"
}
(8/14) Running minio-py tests ... done in 1 minutes and 55 seconds
(9/14) Running s3cmd tests ... done in 26 seconds
(10/14) Running s3select tests ... done in 4 seconds
(11/14) Running versioning tests ... done in 3 minutes and 6 seconds

Executed 11 out of 14 tests successfully.

Deleting image on docker hub
Deleting image locally