Add option to fail if ceph-ansible is not installed

If someone is deploying Ceph then they need ceph-ansible.
The warning might be overlooked and the user may end up
with a message about a missing file. If Ceph is being
deployed then we want to make the validation fail the
deployment if ceph-ansible is not installed so that the
user has a better error message to follow in order to debug.

Also, update warning to refer to the ceph-ansible package.

Change-Id: Ic099c61c74abf6da24a2cce899c944e3bf8ce26b

playbooks/ceph-ansible-installed.yaml

@@ -7,6 +7,7 @@
         Prints a message if ceph-ansible isn't installed
       groups:
         - pre-deployment
+    fail_without_ceph_ansible: false
   tasks:
     - include_role:
         name: ceph

roles/ceph/defaults/main.yml

@@ -0,0 +1,2 @@
+---
+fail_without_ceph_ansible: false

roles/ceph/tasks/ceph-ansible-installed.yaml

@@ -9,6 +9,14 @@
 
 - name: Warn about missing ceph-ansible
   warn:
-    msg: If planning to use Ceph, it is necessary to install the ceph-ansible on the undercloud
+    msg: If planning to use Ceph, it is necessary to install the ceph-ansible package on the undercloud
   when:
     - ceph_ansible_installed.stdout.find('is not installed') != -1
+    - not fail_without_ceph_ansible|default(false)|bool
+
+- name: Fail if ceph-ansible is missing
+  fail:
+    msg: If planning to use Ceph, it is necessary to install the ceph-ansible package on the undercloud
+  when:
+    - ceph_ansible_installed.stdout.find('is not installed') != -1
+    - fail_without_ceph_ansible|default(false)|bool