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

Change-Id: I0e1f7eed0ffe751fa54682103051ad29c08c1517

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.
@@ -212,7 +212,7 @@ conditions:
   neutron_dvr_set:
     not: {equals : [{get_param: NeutronEnableDVR}, '']}
   az_set:
-    not: {equals: [{get_param: NeutronDefaultAvailabilityZones}, '']}
+    not: {equals: [{get_param: NeutronDefaultAvailabilityZones}, []]}
   ovn_and_tls:
     and:
       - contains: ['ovn', {get_param: NeutronMechanismDrivers}]