fix wait issue for old version of bash

tests/nodes/start.sh

@@ -55,6 +55,10 @@ else
     done
 fi
 
-# -n means we will exit when any of the background processes exits.
-# https://www.gnu.org/software/bash/manual/bash.html#index-wait
-wait -n
+# we will exit when any of the background processes exits.
+while true; do
+  for job in $(jobs -p); do
+    wait $job || exit 1
+  done
+  sleep 1
+done