Add posibilitty to configure neutron server default_availability_zones

Closes-Bug: PROD-35166
Change-Id: I6dab42ab6ff75f612ecfbd8638f0354ae8b82f68
diff --git a/README.rst b/README.rst
index 1c3be16..25eb136 100644
--- a/README.rst
+++ b/README.rst
@@ -1796,6 +1796,20 @@
       ....
 
 
+Defining default_availability_zones:
+------------------------------------
+
+Control node:
+
+.. code-block:: yaml
+
+    neutron:
+      ....
+      server:
+        default_availability_zones: 'custom_az1, custom_az2'
+      ....
+
+
 Set nova_metadata_protocol for Neutron
 ---------------------------------------
 
diff --git a/neutron/files/pike/neutron-server.conf b/neutron/files/pike/neutron-server.conf
index 5195503..06c47cb 100644
--- a/neutron/files/pike/neutron-server.conf
+++ b/neutron/files/pike/neutron-server.conf
@@ -113,6 +113,9 @@
 # resource is empty, availability zone is considered for high availability
 # while scheduling the resource. (list value)
 #default_availability_zones =
+{%- if server.default_availability_zones is defined %}
+default_availability_zones = {{ server.default_availability_zones }}
+{%- endif %}
 
 # Maximum number of DNS nameservers per subnet (integer value)
 #max_dns_nameservers = 5
diff --git a/neutron/files/queens/neutron-server.conf b/neutron/files/queens/neutron-server.conf
index d85cea0..0f24cd5 100644
--- a/neutron/files/queens/neutron-server.conf
+++ b/neutron/files/queens/neutron-server.conf
@@ -99,7 +99,9 @@
 # resource is empty, availability zone is considered for high availability
 # while scheduling the resource. (list value)
 #default_availability_zones =
-default_availability_zones = {{ server.availability_zone|default('nova') }}
+{%- if server.default_availability_zones is defined %}
+default_availability_zones = {{ server.default_availability_zones }}
+{%- endif %}
 
 # Maximum number of DNS nameservers per subnet (integer value)
 #max_dns_nameservers = 5