Invoke run_k8s_ansible from its directory

It relies on loading ansible.cfg from the cwd to zero out the
inventory.

Change-Id: I43a8f12eda034d132b6752df29e7b041025f4340

run_k8s_ansible.sh

@@ -40,4 +40,5 @@ export NODE_EXTRA_VOLUME_SIZE="80"
 export USE_OCTAVIA="True"
 export BLOCK_STORAGE_VERSION='v3'
 
-ansible-playbook -v /opt/k8s-on-openstack/site.yaml
+cd /opt/k8s-on-openstack
+ansible-playbook -v site.yaml