BUG/MEDIUM: spoe: Queue message only if no SPOE applet is attached to the stream

If a SPOE applet is already attached to a stream to handle its messages, we must
not queue them. Otherwise it could be handled by another applet leading to
errors. This happens with fragmented messages only. When the first framgnent is
sent, the SPOE applet sending it is attached to the stream. It should be used to
send all other fragments.

This patch must be backported to 1.9 and 1.8.
diff --git a/src/flt_spoe.c b/src/flt_spoe.c
index b820710..a7d6bb9 100644
--- a/src/flt_spoe.c
+++ b/src/flt_spoe.c
@@ -2096,11 +2096,15 @@
 		return -1;
 	}
 
-	/* Add the SPOE context in the sending queue */
-	LIST_ADDQ(&agent->rt[tid].sending_queue, &ctx->list);
+	/* Add the SPOE context in the sending queue if the stream has no applet
+	 * already assigned and wakeup all idle applets. Otherwise, don't queue
+	 * it. */
 	_HA_ATOMIC_ADD(&agent->counters.nb_sending, 1);
 	spoe_update_stat_time(&ctx->stats.tv_request, &ctx->stats.t_request);
 	ctx->stats.tv_queue = now;
+	if (ctx->spoe_appctx)
+		return 1;
+	LIST_ADDQ(&agent->rt[tid].sending_queue, &ctx->list);
 
 	SPOE_PRINTF(stderr, "%d.%06d [SPOE/%-15s] %s: stream=%p"
 		    " - Add stream in sending queue"