Handle repeated C_Initialize and C_Finalize calls

[robin-nitrokey]

According to the spec:

Every call to C_Initialize should (eventually) be succeeded by a single call to C_Finalize.

https://docs.oasis-open.org/pkcs11/pkcs11-spec/v3.1/csd01/pkcs11-spec-v3.1-csd01.html#_Toc98177101

Each application’s call to C_Finalize should be preceded by a single call to C_Initialize

https://docs.oasis-open.org/pkcs11/pkcs11-spec/v3.1/csd01/pkcs11-spec-v3.1-csd01.html#_Toc98177102

C_Initialize should return CKR_CRYPTOKI_ALREADY_INITIALIZED if called twice, and C_Finalize should return CKR_CRYPTOKI_NOT_INITIALIZED if called without a corresponding C_Initialize call.

Currently, we just return CKR_OK in both cases.