Don't use POLL_SERVER_CFN transport for DeployedServer

For config-download we create a set of dummy DeployedServer
resources that has default software_config_transport property
(POLL_SERVER_CFN) which unnecessarily creates ec2 credentials
for these resources. We've dropped heat_cfn service from
undercloud, so change these to use POLL_SERVER_HEAT instead.

Change-Id: Ia86d117299e92e121a69e059b8a8460ef986cdca
(cherry picked from commit 03aa8b10f6)

config-download-software.yaml

@@ -59,6 +59,7 @@ resources:
     type: OS::Heat::DeployedServer
     properties:
       name: server_resource
+      software_config_transport: POLL_SERVER_HEAT
 
 outputs:
 

config-download-structured.yaml

@@ -59,6 +59,7 @@ resources:
     type: OS::Heat::DeployedServer
     properties:
       name: server_resource
+      software_config_transport: POLL_SERVER_HEAT
 
 outputs: