rb: avoid throwing error for force delete of prefix

[poornas]

Description

Motivation and Context

Avoid throwing validation errors for prefix delete
With current master:
➜ bucket git:(master) ✗ mc ls sitea/bucket -r
[2023-01-06 10:52:50 PST] 0B STANDARD 18/
[2023-01-06 10:52:50 PST] 0B STANDARD 1oSHoFb8
➜ bucket git:(master) ✗ mc rb --force sitea/bucket/1oSHoFb8
mc: Failed to remove sitea/bucket/1oSHoFb8. Bucket name bucket/1oSHoFb8 not valid.

With this PR:
➜ mc git:(fxrb) mc rb --force sitea/bucket/1oSHoFb8
Removed sitea/bucket/1oSHoFb8 successfully.
➜ mc git:(fxrb) mc ls sitea/bucket -r
[2023-01-06 10:52:50 PST] 0B STANDARD 18/

How to test this PR?

try to delete prefix via mc rb --force

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