CORD-1877 Only gather facts from build node

Change-Id: If0ab4407c4258d6c966bbacef79f25cbe4ea780f
(cherry picked from commit 13422c2fbf2425411447de640f1ee6bda60cf473)
diff --git a/prep-buildnode-playbook.yml b/prep-buildnode-playbook.yml
index 32f3bd6..bb9d74d 100644
--- a/prep-buildnode-playbook.yml
+++ b/prep-buildnode-playbook.yml
@@ -19,7 +19,7 @@
 # Prep build node to create artifacts
 
 - name: Include vars
-  hosts: all
+  hosts: build
   tasks:
     - name: Include variables
       include_vars: "{{ item }}"