wrongly expect encrypted alerts after ServerHello flight

[Julien00859]

In case siotls acts as a server and that the other side sends an alert (e.g. for a bad certificate) that alert is going to be sent by the client in clear text but at the moment (because we are post ServerHello flight) siotls expects to read encrypted data. Deciphering clear-text just doesn't work.

[Julien00859]

there are bits on the state machine telling that we should ignore the decrypts errors