Fixed AnsibleUnsafeText by converting to int

roles/flannel_register/defaults/main.yaml

@@ -1,6 +1,6 @@
 ---
 flannel_network: "{{ openshift.master.sdn_cluster_network_cidr }}"
-flannel_subnet_len: "{{ 32 - openshift.master.sdn_host_subnet_length }}"
+flannel_subnet_len: "{{ 32 - (openshift.master.sdn_host_subnet_length | int) }}"
 flannel_etcd_key: /openshift.com/network
 etcd_hosts: "{{ etcd_urls }}"
 etcd_conf_dir: "{{ openshift.common.config_base }}/master"