Update atomic-openshift-master.j2

roles/openshift_master/templates/atomic-openshift-master.j2

@@ -1,6 +1,6 @@
 OPTIONS=--loglevel={{ openshift.master.debug_level | default(2) }}
 CONFIG_FILE={{ openshift_master_config_file }}
-{% if openshift_push_via_dns %}
+{% if openshift_push_via_dns | default(false) %}
 OPENSHIFT_DEFAULT_REGISTRY=docker-registry.default.svc:5000
 {% endif %}
 {% if openshift.common.is_containerized | bool %}