reset() not working correctly

[brycx]

Currently reset() checks whether or not the state is already finalized. If it is not finalized, it will not reset the state. So if someone were to call reset() not having finalized the state before, incorrect results would be produced. Such streaming states include hmac, poly1305, blake2b and cshake.

[brycx]

In case of hmac, reset() did not take into account either that the Sha512 object would not reset itself when reset() would be called after an update() with no finalization. This is fixed in 982b84c.