seed: Disable SNAT configuration by default

Introduce seed_enable_snat and change default to false.

Change-Id: I0fde948a306ef9b8cf9525f1e93650d36d5f14f6

ansible/group_vars/all/seed

@@ -23,6 +23,9 @@ seed_default_network_interfaces: >
 # List of extra networks to which seed nodes are attached.
 seed_extra_network_interfaces: []
 
+# Whether to enable SNAT on seed nodes. Default is false.
+seed_enable_snat: false
+
 ###############################################################################
 # Seed node software RAID configuration.
 

ansible/ip-routing.yml

@@ -7,3 +7,4 @@
     - ip-routing
   roles:
     - role: ip-routing
+      when: seed_enable_snat | bool

ansible/snat.yml

@@ -11,3 +11,4 @@
         source_ip: "{{ ansible_facts.default_ipv4.address }}"
   roles:
     - role: snat
+      when: seed_enable_snat | bool

etc/kayobe/seed.yml

@@ -18,6 +18,9 @@
 # List of extra networks to which seed nodes are attached.
 #seed_extra_network_interfaces:
 
+# Whether to enable SNAT on seed nodes. Default is false.
+#seed_enable_snat:
+
 ###############################################################################
 # Seed node software RAID configuration.
 

releasenotes/notes/seed-disable-snat-4d1e7899456f7561.yaml

+---
+features:
+  - |
+    Adds a new variable ``seed_enable_snat`` that allows users to enable SNAT
+    service on the seed. The default value is ``false``.