Add host_routes to port_from_pool.j2

Add the host_routes as output of the fake neutron ports
created by legacy predictable IPs templates.

Closes-Bug: #1792968
Change-Id: Ie330635fa551d8406a1bf082c89f7c58d82088d6
(cherry picked from commit 711f7ef711)

network/ports/port_from_pool.j2

@@ -78,4 +78,7 @@ outputs:
       - - {get_param: [IPPool, {get_param: {{network.name}}NetName}, {get_param: NodeIndex}]}
         - '/'
         - {str_split: ['/', {get_param: {{network.name}}NetCidr}, 1]}
+  host_routes:
+    description: Host routes of the ports subnet
+    value: {{network.routes|default([])}}
 

releasenotes/notes/fix-port-from-pool-host-routes-7fcc4d00cb11603d.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Fixes an issue in the legacy port_from_pool templates for predictable IP
+    addressing. Prior to this fix using these tamplates would fail with the
+    following error: **Referenced Attribute (%network_name%%Port host_routes)
+    is incorrect.** (Bug: `1792968
+    <https://bugs.launchpad.net/tripleo/+bug/1792968>`_.)