cosmetic: Hide mc admin bucket and its subcommands visible

[vadmeste]

Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

Current mc admin bucket is visible under 'mc admin' however, mc admin bucket
will not show sub-commands, which is confusing.

Hide mc admin bucket and make mc admin bucket subcommands visible for now,
until removed later.

Motivation and Context

How to test this PR?

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