Add pre checks before installing instance HA

This commit is the first of two that will try to make the instance HA
procedure idempotent. This first one adds pre checks that make the
procedure fail if there are already IHA resources or STONITH resources
inside the cluster.

Change-Id: Ib481f7be119ffd301e53d952c413f1ba0e05de84

roles/instance-ha/tasks/main.yml

@@ -1,4 +1,9 @@
 ---
+- name: Check if Instance HA steps were already applied
+  include: pre-checks.yml
+  when:
+    - instance_ha_action == "install"
+
 - name: Apply STONITH for controller nodes
   include_role:
     name: stonith-config

roles/instance-ha/tasks/pre-checks.yml

@@ -0,0 +1,25 @@
+---
+- block:
+  - name: Check if STONITH resources already exist
+    shell: |
+      pcs stonith show | grep {{ item }}
+    with_items:
+      - fence-nova
+    register: pre_existing_stonith
+    failed_when: pre_existing_stonith.rc == 0
+
+  - name: Check if IHA resources already exist
+    shell: |
+      pcs resource show | grep "{{ item }}"
+    with_items:
+      - compute-unfence-trigger
+      - nova-compute-checkevacuate
+      - nova-compute
+      - nova-evacuate
+      - neutron-openvswitch-agent-compute
+      - libvirtd-compute
+      - ceilometer-compute
+    register: pre_existing_resources
+    failed_when: pre_existing_resources.rc == 0
+  become: yes
+  delegate_to: "{{ groups.controller[0] }}"