Convert generator to list in Heat list API call

The generator being returned by heatclient didn't like
being iterated multiple times (as when doing a multiple
delete through the stacks table).

Fixes bug #1224393

Change-Id: I01482c0fadcf145fe99806983d9a1dc6f50ac56a

openstack_dashboard/api/heat.py

@@ -53,7 +53,7 @@ def heatclient(request, password=None):
 
 
 def stacks_list(request):
-    return heatclient(request).stacks.list()
+    return [stack for stack in heatclient(request).stacks.list()]
 
 
 def stack_delete(request, stack_id):