message: restarter: exit 1 when child has abnormal exit
  When Envoy dies, for example when there is an invalid config schema, it
  should exit nonzero to indicate that something went wrong.
diff: @@ -98,7 +98,7 @@ def sigchld_handler(signum, frame):
  # Our last child died, so we have no purpose. Exit.
  if not pid_list:
  print "exiting due to lack of child processes"
  - sys.exit(0)
  + sys.exit(1 if kill_all_and_exit else 0)
  def fork_and_exec():
  