fix type conversion in UpdateKey for Vault

[aead]

Description

This commit fixes a type conversion in the UpdateKey
implementation of Vault.

Motivation and Context

Thanks to @sinhaashish

How to test this PR?

Setup Vault: https://github.com/minio/minio/tree/master/docs/kms
Pull: #7955
Start a MinIO server with Vault configuration and configure /pkg/madmin/examples/key-status.go with the correct access/secret key.
Run: go run github.com/minio/minio/pkg/madmin/examples/key-status.go

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• 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)
• Documentation needed
• Unit tests needed
• Functional tests needed (If yes, add mint PR # here: )

[minio-ops]

Mint Automation

Test	Result
mint-compression-xl.sh	✔️
mint-compression-dist-xl.sh	✔️
mint-compression-fs.sh	✔️
mint-worm.sh	✔️
mint-fs.sh	✔️
mint-dist-xl.sh	✔️
mint-gateway-nas.sh	✔️
mint-xl.sh	❌ more...
mint-large-bucket.sh	❌ more...

8058-f6f54e2/mint-xl.sh.log:

Running with
SERVER_ENDPOINT:      72.28.97.57:31657
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

To get logs, run 'docker cp b734a22d3b39:/mint/log /tmp/mint-logs'

(1/14) Running aws-sdk-go tests ... FAILED in 13 seconds
{
  "alert": "",
  "args": {
    "bucketName": "aws-sdk-go-test-nvyapgl24aqv03",
    "expiry": 60000000000,
    "objectName": "presignedTest"
  },
  "duration": 12582,
  "error": "RequestError: send request failed\ncaused by: Put http://72.28.97.57:31657/aws-sdk-go-test-nvyapgl24aqv03: dial tcp 72.28.97.57:31657: connect: no route to host",
  "function": "PresignedPut",
  "message": "AWS SDK Go CreateBucket Failed",
  "name": "aws-sdk-go",
  "status": "FAIL"
}

Executed 0 out of 14 tests successfully.

8058-f6f54e2/mint-large-bucket.sh.log:

Running with
SERVER_ENDPOINT:      72.28.97.54:30136
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

To get logs, run 'docker cp 1486ef65918f:/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 2 seconds
(3/14) Running aws-sdk-php tests ... done in 1 minutes and 3 seconds
(4/14) Running aws-sdk-ruby tests ... done in 12 seconds
(5/14) Running awscli tests ... done in 2 minutes and 23 seconds
(6/14) Running healthcheck tests ... done in 2 seconds
(7/14) Running mc tests ... FAILED in 2 minutes and 22 seconds
{
  "name": "mc",
  "duration": "106886",
  "function": "test_mirror_list_objects_storage_class",
  "status": "FAIL",
  "error": "/mint/run/core/mc/mc --config-dir /tmp/.mc-7170 --quiet --no-color mirror --storage-class REDUCED_REDUNDANCY /mint/data myminio/mc-test-bucket-17097  >>> \n`/mint/data/datafile-1-MB` -> `myminio/mc-test-bucket-17097/datafile-1-MB`\n`/mint/data/datafile-0-b` -> `myminio/mc-test-bucket-17097/datafile-0-b`\n`/mint/data/datafile-1-kB` -> `myminio/mc-test-bucket-17097/datafile-1-kB`\n`/mint/data/datafile-1-b` -> `myminio/mc-test-bucket-17097/datafile-1-b`\n`/mint/data/datafile-10-MB` -> `myminio/mc-test-bucket-17097/datafile-10-MB`\n`/mint/data/datafile-100-kB` -> `myminio/mc-test-bucket-17097/datafile-100-kB`\n`/mint/data/datafile-1.03-MB` -> `myminio/mc-test-bucket-17097/datafile-1.03-MB`\n`/mint/data/datafile-129-MB` -> `myminio/mc-test-bucket-17097/datafile-129-MB`\n`/mint/data/datafile-10-kB` -> `myminio/mc-test-bucket-17097/datafile-10-kB`\n`/mint/data/datafile-11-MB` -> `myminio/mc-test-bucket-17097/datafile-11-MB`\n`/mint/data/datafile-5-MB` -> `myminio/mc-test-bucket-17097/datafile-5-MB`\n`/mint/data/datafile-6-MB` -> `myminio/mc-test-bucket-17097/datafile-6-MB`\n`/mint/data/datafile-33-kB` -> `myminio/mc-test-bucket-17097/datafile-33-kB`\n`/mint/data/datafile-5243880-b` -> `myminio/mc-test-bucket-17097/datafile-5243880-b`\n`/mint/data/datafile-65-MB` -> `myminio/mc-test-bucket-17097/datafile-65-MB`\nmc: <ERROR> Failed to copy `/mint/data/datafile-65-MB`. Please reduce your request\nmc: <ERROR> Failed to copy `/mint/data/datafile-10-MB`. Please reduce your request\nmc: <ERROR> Failed to copy `/mint/data/datafile-11-MB`. Please reduce your request\nmc: <ERROR> Failed to copy `/mint/data/datafile-129-MB`. Please reduce your request\nTotal: 233.17 MiB, Transferred: 496.36 MiB, Speed: 4.65 MiB/s"
}

Executed 6 out of 14 tests successfully.

[codecov-io]

Codecov Report

Merging #8058 into master will increase coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #8058      +/-   ##
==========================================
+ Coverage   45.02%   45.02%   +<.01%     
==========================================
  Files         321      321              
  Lines       51387    51387              
==========================================
+ Hits        23137    23138       +1     
+ Misses      26098    26097       -1     
  Partials     2152     2152

Impacted Files	Coverage Δ
cmd/crypto/vault.go	11.25% <0%> (ø)	⬆️
cmd/fs-v1.go	61.06% <0%> (-0.38%)	⬇️
pkg/certs/certs.go	58.76% <0%> (+4.12%)	⬆️

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[sinhaashish]

LGTM