[Housekeeping] Close system port when jobs are cancelled (#182)

* Created a test setup that works

* Refactored test setup into real-world fixes

priv/cmd_wrapper.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+# This script is a wrapper for other programs
+# that ensures they are killed when stdin closes
+# (eg: a job terminates)
+
+# Start the program in the background
+exec "$@" &
+pid1=$!
+
+# Silence warnings from here on
+exec >/dev/null 2>&1
+
+# Read from stdin in the background and
+# kill running program when stdin closes
+exec 0<&0 $(
+  while read; do :; done
+  kill -KILL $pid1
+) &
+pid2=$!
+
+# Clean up
+wait $pid1
+ret=$?
+kill -KILL $pid2
+exit $ret