BUG/MINOR: stream-int: Process connection/CS errors first in si_cs_send()

Errors on the connections or the conn-stream must always be processed in
si_cs_send(), even if the stream-interface is already subscribed on
sending. This patch does not fix any concrete bug per-se. But it is required by
the following one to handle those errors during synchronous sends.

This patch must be backported with the following one to 2.0 and probably to 1.9
too, but with caution because the code is really different.

(cherry picked from commit 328ed220a8c5211aa8b6f37b982f319cf6b3f3d1)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 7d89cc9..4130444 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -652,10 +652,6 @@
 	int ret;
 	int did_send = 0;
 
-	/* We're already waiting to be able to send, give up */
-	if (si->wait_event.events & SUB_RETRY_SEND)
-		return 0;
-
 	if (conn->flags & CO_FL_ERROR || cs->flags & (CS_FL_ERROR|CS_FL_ERR_PENDING)) {
 		/* We're probably there because the tasklet was woken up,
 		 * but process_stream() ran before, detected there were an
@@ -669,6 +665,10 @@
 		return 1;
 	}
 
+	/* We're already waiting to be able to send, give up */
+	if (si->wait_event.events & SUB_RETRY_SEND)
+		return 0;
+
 	/* we might have been called just after an asynchronous shutw */
 	if (conn->flags & CO_FL_SOCK_WR_SH || oc->flags & CF_SHUTW)
 		return 1;