[DEV] Update SMD to support crytpographic enrollment and attestation

[alexlovelltroy]

Nodes with TPMs can attest their own identity using a process documented and implemented in the go-attestation library from google. In order to verify the attestation records, a public key or CA certificate is required.

Since SMD is the main inventory service for OpenCHAMI it makes sense to add the Enrollment Key for each node to SMD and link it to the node through the boot MAC. When a node is replaced, the xname remains the same, but the boot mac and the EK will change.