this change uses the new storj/common noise helpers, which:
* add a security fix (require an expected node id for validating
noise key attestations)
* stops doing an unnecessary order signature validation (it's
already been done inside of PutPiece)
* removes some duplicate code
Change-Id: I5e67a08ff216cd9c5b0b82e40b4d9de664b6b0fc