Improve handling of writing to /etc/default/spinnaker.
Improve handling of writing to /etc/default/spinnaker.

tgracchus/spinnaker,ewiseblatt/spinnaker,stitchfix/spinnaker,tgracchus/spinnaker,duftler/spinnaker,spinnaker/spinnaker,imosquera/spinnaker,skim1420/spinnaker,skim1420/spinnaker,ewiseblatt/spinnaker,spinnaker/spinnaker,imosquera/spinnaker,duftler/spinnaker,jtk54/spinnaker,jtk54/spinnaker,jtk54/spinnaker,Roshan2017/spinnaker,imosquera/spinnaker,ewiseblatt/spinnaker,ewiseblatt/spinnaker,stitchfix/spinnaker,skim1420/spinnaker,duftler/spinnaker,tgracchus/spinnaker,spinnaker/spinnaker,skim1420/spinnaker,Roshan2017/spinnaker,Roshan2017/spinnaker,duftler/spinnaker,stitchfix/spinnaker,spinnaker/spinnaker