Let Nexus decide how to deal with old partitions on new U.2s

[smklein]

This will be necessary to resolve issues like #5128

Blocked by #5150 and #5151

When Nexus chooses to adopt a new physical disk into the control plane, it will have an opportunity to make a decision about "what to do with old partitions on this device". As we've seen in #5128 , not all U.2s will have uniform decisions, and it may make sense to overwrite them or ask an operator for additional input before proceeding.

[davepacheco]

@smklein I think this is not a blocker for the Q1 milestone. Is that right?

[smklein]

@smklein I think this is not a blocker for the Q1 milestone. Is that right?

Correct - we could opt to have a strict "only adopt disks which have a specific, well-formed partition table" policy to start, and still provide the ability to arbitrarily expunge disks.