Fix grenade shutdown script
Fix grenade shutdown script

Due to some fix in devstack, using the old lib/heat library doesn't work
anymore, so let's replicate the stop_heat function.

Change-Id: I8e7c62962cef29e35c37ad98a1646630388fb4ab
Closes-Bug: #1506462

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