fix wait issue in start.sh

tests/nodes/start.sh

@@ -56,9 +56,13 @@ else
 fi
 
 # we will exit when any of the background processes exits.
+# we don't use `wait -n` because of compatibility issues between bash and zsh
+initial_jobs=$(jobs -p | wc -l)
 while true; do
-  for job in $(jobs -p); do
-    wait $job || exit 1
-  done
-  sleep 1
+    current_jobs=$(jobs -p | wc -l)
+    if [ "$current_jobs" -lt "$initial_jobs" ]; then
+        echo "A background job has exited, exiting ..."
+        exit 1
+    fi
+    sleep 1
 done