Make default of NeutronDefaultAvailabilityZones empty array

NeutronDefaultAvailabilityZones is of type comma_delimited_list
therefore the default need to be [] instead of ''. Right now
the condition checks for empty string which is not the case
for comma_delimited_list and the hieradata covered by the
az_unset condition get always set.

Closes-Bug: #1934970

Conflicts:
    deployment/neutron/neutron-api-container-puppet.yaml

Change-Id: I0e1f7eed0ffe751fa54682103051ad29c08c1517
(cherry picked from commit f276e7a)

deployment/neutron/neutron-api-container-puppet.yaml

@@ -138,7 +138,7 @@ parameters:
                  be used by Neutron if its resource is created without
                  availability zone hints. If not set, no AZs will be configured
                  for Neutron network services.
-    default: ''
+    default: []
     type: comma_delimited_list
   NeutronNetworkSchedulerDriver:
     description: The network schedule driver to use for avialability zones.
@@ -203,7 +203,7 @@ conditions:
   internal_tls_enabled: {equals: [{get_param: EnableInternalTLS}, true]}
   neutron_dvr_unset: {equals : [{get_param: NeutronEnableDVR}, '']}
   is_ovn_in_neutron_mechanism_driver: {contains: ['ovn', {get_param: NeutronMechanismDrivers}]}
-  az_unset: {equals: [{get_param: NeutronDefaultAvailabilityZones}, '']}
+  az_unset: {equals: [{get_param: NeutronDefaultAvailabilityZones}, []]}
   ovn_and_tls: {and: [is_ovn_in_neutron_mechanism_driver, internal_tls_enabled]}
   enable_sqlalchemy_collectd: {equals : [{get_param: EnableSQLAlchemyCollectd}, true]}
   key_size_override_unset: {equals: [{get_param: NeutronCertificateKeySize}, '']}