[pa,spm] add RPC to retrieve a raw token from the SPM/HSM

[timothytrippel]

The CP flows require the ability to retrieve the RawUnlock token from the SPM. We need to add an RPC to the PA/SPM to retrieve a pre-provisioned token from the HSM:

• add GetStoredToken RPCs to
  • PA
  • SPM
• implement SPM function to retrieve a raw token from persistent storage
• update hsmtool config to inject RawUnlock token into SPM HSMs