DTLS message_sequence number wrong in rehandshake ServerHello

This fix ensures that
* A HelloRequest is retransmitted if not responded by a ClientHello
* The HelloRequest "consumes" the sequence number 0. The subsequent
ServerHello uses the sequence number 1.
* The client also expects the sequence number of the ServerHello to
be 1 if a HelloRequest was received earlier.
This patch fixes the RFC violation.

ssl/d1_pkt.c

@@ -1058,6 +1058,7 @@ start:
 			!(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS) &&
 			!s->s3->renegotiate)
 			{
+			s->d1->handshake_read_seq++;
 			s->new_session = 1;
 			ssl3_renegotiate(s);
 			if (ssl3_renegotiate_check(s))

ssl/d1_srvr.c

@@ -294,10 +294,11 @@ int dtls1_accept(SSL *s)
 		case SSL3_ST_SW_HELLO_REQ_B:
 
 			s->shutdown=0;
+			dtls1_clear_record_buffer(s);
 			dtls1_start_timer(s);
 			ret=ssl3_send_hello_request(s);
 			if (ret <= 0) goto end;
-			s->s3->tmp.next_state=SSL3_ST_SW_HELLO_REQ_C;
+			s->s3->tmp.next_state=SSL3_ST_SR_CLNT_HELLO_A;
 			s->state=SSL3_ST_SW_FLUSH;
 			s->init_num=0;