RA dev guide: fix example code for stop action
RA dev guide: fix example code for stop action

A resource may be stopped while it's in Master mode. Fix the example
code so the resource is demoted before stopping.

asp24/resource-agents,stevenraspudic/resource-agents,asp24/resource-agents,asp24/resource-agents,stevenraspudic/resource-agents,stevenraspudic/resource-agents