Make all lookup plugins work with lists

Lookup plugins should accept a string or a list, and always return
a list, even if it is just one item.

lib/ansible/runner/lookup_plugins/items.py

@@ -21,7 +21,6 @@ class LookupModule(object):
         pass
 
     def run(self, terms, **kwargs):
-        return terms
-
-
-
+        if isinstance(terms, basestring):
+            terms = [ terms ]
+        return [term for term in terms]