Revert "Vars specified via CLI have the highest priority."

Reverting as this as reported allows some variables to clobber each other.
We'll work on a different fix.

This reverts commit c5469f6367.

lib/ansible/playbook/play.py

@@ -189,8 +189,9 @@ class Play(object):
         else:
             raise errors.AnsibleError("'vars_prompt' section is malformed, see docs")
 
-        vars.update(self.playbook.extra_vars)
-        return vars
+        results = self.playbook.extra_vars.copy()
+        results.update(vars)
+        return results
 
     # *************************************************