Add grenade job

This patch set adds grenade support to Watcher based on
legacy-dsvm-base job.

Change-Id: I9e23f59f7415aa350b2da644d8801621533b69b0

playbooks/legacy/grenade-devstack-watcher/post.yaml

@@ -0,0 +1,15 @@
+- hosts: primary
+  tasks:
+
+    - name: Copy files from {{ ansible_user_dir }}/workspace/ on node
+      synchronize:
+        src: '{{ ansible_user_dir }}/workspace/'
+        dest: '{{ zuul.executor.log_root }}'
+        mode: pull
+        copy_links: true
+        verify_host: true
+        rsync_opts:
+          - --include=/logs/**
+          - --include=*/
+          - --exclude=*
+          - --prune-empty-dirs