dtls: change to state closing when sending a fatal alert

When we send a fatal alert we can not recover and a new connection
should be established.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: send no alert when we do not have a peer

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: call init_cipher() in calculate_key_block()

init_cipher() was always called directly after calculate_key_block(),
now the call is moved into calculate_key_block().
This also moves init_cipher() in front of calculate_key_block().

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: call dtls_debug_keyblock() in in calculate_key_block()

It was called with the same input twice, this is not needed.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>