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

When the cli 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.

This patch should fix the issue #2107. It is 2.8-specific. No backport
needed.
diff --git a/src/cli.c b/src/cli.c
index 0849cbe..820a45a 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -893,8 +893,10 @@
 	int reql;
 	int len;
 
-	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)))) {
+		co_skip(sc_oc(sc), co_data(sc_oc(sc)));
 		goto out;
+	}
 
 	/* Check if the input buffer is available. */
 	if (!b_size(&res->buf)) {