Attributes START_DATE and END_DATE are not ciphered in a private key #655

Hello,

While developing a product for which we have to support multiple HSM, we encountered a problem in SoftHSM with the START_DATE and END_DATE attrtibutes for private keys.
It is a case that is supported by the spec but from what I understand, SoftHSM expects that START_DATE and END_DATE are only set for public keys.
When set on private keys and reloading the private key and reading the _DATE attributes, it tries to decrypt them but fails in IV reading since they are not encrypted to begin with.