So far we assumes that metadata key/nonce cannot be empty at all
but at some point we adjusted code to accept empty metadata/key/nonce
to save DB space.
This change is adjusting how we are processing nonce while
FinishMoveObject/FinishCopyObject. We can use storj.Nonce directly
which makes code cleaner. It's also fixing issue in FinishMoveObject
where we didn't convert nonce correctly to []byte.
Part of change is disabling validation for key and nonce until
uplink will be adjusted. We need change uplink to send always
both key and nonce or non of them. Validation will be restored
as soon as change for uplink will be merged.
https://github.com/storj/storj/issues/4646
Change-Id: Ia1772bc430ae591f54c6a9ae0308a4968aa30bed
4da3dc8170