Fix bashisms in k8s os config template fragment.

Partial fix for problems output by checkbashisms for file
magnum/templates/kubernetes/fragments/write-kube-os-config.sh only.

Change-Id: I68b021da63b6c2d058053023a4fa26d643f0134b
Partial-Bug: #1561232

magnum/templates/kubernetes/fragments/write-kube-os-config.sh

@@ -5,7 +5,7 @@
 KUBE_OS_CLOUD_CONFIG=/etc/sysconfig/kube_openstack_config
 
 # kubernetes backend only support keystone v2 at this point
-AUTH_URL=${AUTH_URL/v3/v2}
+AUTH_URL=$(echo "$AUTH_URL" | tr -s "v3" "v2")
 
 # Generate a the configuration for Kubernetes services
 # to talk to OpenStack Neutron