BUG/MEDIUM: lua: fix a segfault in txn:done() if called twice

When called from an http ruleset, txn:done() can still crash the process
because it closes the stream without consuming pending data resulting in
the transaction's buffer representation to differ from the real buffer.

This patch also adjusts the transaction's state to indicate that it's
closed to be consistent with what's already done in redirect rules.
diff --git a/src/hlua.c b/src/hlua.c
index ffcfb83..aa23696 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -3655,6 +3655,28 @@
 	ic = &htxn->s->req;
 	oc = &htxn->s->res;
 
+	if (htxn->s->txn) {
+		/* HTTP mode, let's stay in sync with the stream */
+		bi_fast_delete(ic->buf, htxn->s->txn->req.sov);
+		htxn->s->txn->req.next -= htxn->s->txn->req.sov;
+		htxn->s->txn->req.sov = 0;
+		ic->analysers &= AN_REQ_HTTP_XFER_BODY;
+		oc->analysers = AN_RES_HTTP_XFER_BODY;
+		htxn->s->txn->req.msg_state = HTTP_MSG_CLOSED;
+		htxn->s->txn->rsp.msg_state = HTTP_MSG_DONE;
+
+		/* Trim any possible response */
+		oc->buf->i = 0;
+		htxn->s->txn->rsp.next = htxn->s->txn->rsp.sov = 0;
+
+		/* Note that if we want to support keep-alive, we need
+		 * to bypass the close/shutr_now calls below, but that
+		 * may only be done if the HTTP request was already
+		 * processed and the connection header is known (ie
+		 * not during TCP rules).
+		 */
+	}
+
 	channel_auto_read(ic);
 	channel_abort(ic);
 	channel_auto_close(ic);