Propage errors in post test hook
Propage errors in post test hook

If prepare scripts fail, we don't want to run the tests. Add error
option to exit early.

Change-Id: I23a0f51f8252beee7c1cd7a9bdf2002884266a71

openstack/heat,noironetworks/heat,cwolferh/heat-scratch,openstack/heat,noironetworks/heat,cwolferh/heat-scratch