Make start return 0 if the service is already started.
Make start return 0 if the service is already started.

borntyping/cookbook-supervisor,joeheung/supervisor,h4ck3rm1k3/supervisor,greenbits/supervisor,h4ck3rm1k3/supervisor,GannettDigital/chef-supervisor,greenbits/supervisor,poise/supervisor,greenbits/supervisor,poise/supervisor,GannettDigital/chef-supervisor,rstudio/supervisor,joeheung/supervisor,channelgrabber/supervisor,h4ck3rm1k3/supervisor,borntyping/cookbook-supervisor,knowsis/supervisor,rstudio/supervisor,corbel-platform/supervisor,corbel-platform/supervisor,channelgrabber/supervisor,GannettDigital/chef-supervisor,borntyping/cookbook-supervisor,channelgrabber/supervisor,joeheung/supervisor,corbel-platform/supervisor,rstudio/supervisor,poise/supervisor