ignore checksum validation while fetching key

This ansible task is failing while fetching keys for
multiple hypervisors when the deployment is using VMs
on multi hypervisors for overcloud deployment.
So we disable checksum validation for multi hypervisor
environment.

GH-397

Change-Id: Ic6b47510ee02668e688bf4148dd02fc018983b98

plugins/virsh/prepare_hypervisor.yml

@@ -127,10 +127,13 @@
       when: not result.stat.exists | bool
 
     - name: copy server private key from hypervisor for SSH proxy
+      vars:
+          validate_checksum:  "{{ (groups.hypervisor|count == 1) | ternary('yes', 'no') }}"
       fetch:
           src: "{{ item.src }}"
           dest: "{{ item.dest }}"
           flat: yes
+          validate_checksum: "{{ validate_checksum }}"
       with_items:
           - {src: "~/.ssh/id_rsa", dest: "{{ inventory_dir }}/id_rsa"}
           - {src: "~/.ssh/id_rsa.pub", dest: "{{ inventory_dir }}/id_rsa.pub"}