Make sure VARS_CACHE for hosts are updated with the play vars too

Fixes #6979

lib/ansible/playbook/play.py

@@ -855,4 +855,5 @@ class Play(object):
 
         # finally, update the VARS_CACHE for the host, if it is set
         if host is not None:
+            self.playbook.VARS_CACHE[host].update(self.vars)
             self.playbook.VARS_CACHE[host].update(self.playbook.extra_vars)