Fix don't zero_label when replace with spare

[tuxoko]

When replacing a disk with non-wholedisk spare, we shouldn't zero_label
it. The wholedisk case already skip it. In fact, zero_label function
will fail saying device busy because it's already opened exclusively,
but since there's no error checking, the replace command will succeed,
causing great confusion.

Signed-off-by: Chunwei Chen david.chen@osnexus.com

Note: split from #6277

Description

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
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