BUG/MEDIUM: stats: Eat output data when waiting for appctx shutdown

When the stats applet is executed while a shut is pending, the remaining
output data must always be consumed. Otherwise, this can prevent the stream
to exit, leading to a spinning loop on the applet.

It is 2.8-specific. No backport needed.
diff --git a/src/stats.c b/src/stats.c
index 18a5f01..0fa2df3 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -4459,8 +4459,10 @@
 
 	res_htx = htx_from_buf(&res->buf);
 
-	if (unlikely(se_fl_test(appctx->sedesc, (SE_FL_EOS|SE_FL_ERROR|SE_FL_SHR|SE_FL_SHW))))
+	if (unlikely(se_fl_test(appctx->sedesc, (SE_FL_EOS|SE_FL_ERROR|SE_FL_SHR|SE_FL_SHW)))) {
+		appctx->st0 = STAT_HTTP_END;
 		goto out;
+	}
 
 	/* Check if the input buffer is available. */
 	if (!b_size(&res->buf)) {