Fix outdated link in sample plugin
Fix outdated link in sample plugin

Link in sample_plugin.py is outdated
and is changed

Change-Id: I2f3a7b59c6380e4584a8ce2a5313fe766a40a52a
Closes-Bug: #1491975

openstack/heat,gonzolino/heat,pratikmallya/heat,gonzolino/heat,dragorosson/heat,steveb/heat,pratikmallya/heat,takeshineshiro/heat,maestro-hybrid-cloud/heat,dims/heat,takeshineshiro/heat,cwolferh/heat-scratch,jasondunsmore/heat,cwolferh/heat-scratch,jasondunsmore/heat,openstack/heat,noironetworks/heat,maestro-hybrid-cloud/heat,noironetworks/heat,dims/heat,steveb/heat,dragorosson/heat