CI: monasca: ignore exited monasca_thresh container

Ignore the monasca_thresh container if it is listed as exited.
The container was recently changed to operate as a 'one shot' container,
submitting a job to storm then exiting. This does not fit with the
usual pattern of Kolla Ansible container usage, but is harmless.

Depends-On: https://review.opendev.org/c/openstack/kolla/+/812203

Change-Id: Id40d2260a67ef604255fb1818d41cdcbc73164d7
(cherry picked from commit 3b22d33)

Author: markgoddard

tests/check-failure.sh

@@ -23,11 +23,17 @@ check_failure() {
     unhealthy_containers=$(sudo docker ps -a --format "{{.Names}}" \
         --filter health=unhealthy)
 
-    if [[ -n "$failed_containers" ]]; then
+    if [[ -n "$unhealthy_containers" ]]; then
         exit 1;
     fi
 
-    if [[ -n "$unhealthy_containers" ]]; then
+    # NOTE(mgoddard): monasca-thresh is a one-shot container that exits but
+    # remains in place, leaving it with a status of exited. This is harmless.
+    if [[ "$failed_containers" = "monasca_thresh" ]]; then
+        exit 0
+    fi
+
+    if [[ -n "$failed_containers" ]]; then
         exit 1;
     fi
 }