Convert DTLSv1_listen to use new state machine code

The DTLSv1_listen code set the state value explicitly to move into init.
Change to use state_set_in_init() instead.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

ssl/d1_lib.c

@@ -868,11 +868,8 @@ int dtls1_listen(SSL *s, struct sockaddr *client)
      */
     SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
 
-    /*
-     * Put us into the "init" state so that dtls1_accept doesn't clear our
-     * state
-     */
-    s->state = SSL_ST_ACCEPT;
+    /* Put us into the "init" state so that we don't get our state cleared */
+    statem_set_in_init(s, 1);
 
     if(BIO_dgram_get_peer(rbio, client) <= 0) {
         SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);