cloud_config: Add bash header to swarm script
cloud_config: Add bash header to swarm script

This patch adds "#!/bin/sh" to the swarm shortcut so that it can
be recognized as a valid script by Go's os/exec.

PenguinToast/quilt,LuiseV/quilt,NetSys/quilt,kklin/kelda,stevenlin598/quilt,NetSys/quilt,mmussomele/quilt,akshayknarayan/quilt,ejj/quilt-dev,akshayknarayan/quilt,kklin/kelda,akshayknarayan/quilt,kklin/quilt,ZhongtianWang/quilt,PenguinToast/quilt,ZhongtianWang/quilt,LuiseV/quilt,kklin/quilt,LuiseV/quilt,stevenlin598/quilt,tejasmanohar/quilt,kklin/quilt,mmussomele/quilt,mmussomele/quilt,mmussomele/quilt,LuiseV/quilt,secant/quilt,stevenlin598/quilt,PenguinToast/quilt,kayousterhout/quilt,stevenlin598/quilt,tejasmanohar/quilt,kelda/kelda,quilt/quilt,ZhongtianWang/quilt,quilt/quilt,quilt/quilt,tejasmanohar/quilt,secant/quilt,NetSys/quilt,quilt/quilt,ZhongtianWang/quilt,PenguinToast/quilt,secant/quilt,PenguinToast/quilt,ejj/quilt-dev,kayousterhout/quilt,NetSys/quilt,mmussomele/quilt,kayousterhout/quilt,akshayknarayan/quilt,ejj/quilt-dev,kklin/quilt,stevenlin598/quilt,kelda/kelda,kklin/kelda,kelda/kelda,kklin/kelda,stevenlin598/quilt,mmussomele/quilt,secant/quilt,LuiseV/quilt,kelda/kelda,kayousterhout/quilt,tejasmanohar/quilt,secant/quilt,NetSys/quilt,ejj/quilt-dev