fix unset defaults

kolla/node_custom_config/nova.conf

@@ -26,7 +26,9 @@ workers = 10
 [filter_scheduler]
 # Override default filters (just remove filters not relevant to baremetal-only)
 # default: RetryFilter,AvailabilityZoneFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter,BlazarFilter
+{% if nova_enabled_filters is defined %}
 enabled_filters = {{ nova_enabled_filters }}
+{% endif %}
 # https://docs.openstack.org/ironic/rocky/install/configure-compute.html
 # > Enables querying of individual hosts for instance information.
 #   Not possible for bare metal nodes, so set it to False.
@@ -138,6 +140,3 @@ rbd_secret_uuid = {{ rbd_secret_uuid }}
 {% endif %}
 virt_type = {{ nova_compute_virt_type }}
 {% endif %}
-#{% if nova_libvirt_cpu_mode %}
-#cpu_mode = {{ nova_libvirt_cpu_mode }}
-#{% endif %}