[IR plugin] source dir should be found on localhost

tobiko-ir-deploy was not correctly performed because the source
directory was not found
IR jobs not specifying tobiko-refspec could not execute tobiko tests
successfully due to this

Change-Id: Ic516d9df0dfb95e0c62dca00774242abf4684e9d

infrared_plugin/roles/tobiko-ir-deploy/tasks/main.yaml

@@ -32,6 +32,7 @@
     - checkout_files is skipped
   block:
     - name: "check source directory exists"
+      delegate_to: localhost
       stat:
         path: '{{ deploy_src_dir }}'
       register: deploy_src_dir_stat