Fix 'sequence' plugin error.

If 'terms' is a string, replace it with a single item list.

lib/ansible/runner/lookup_plugins/sequence.py

@@ -175,6 +175,9 @@ class LookupModule(object):
 
         terms = utils.listify_lookup_plugin_terms(terms, self.basedir, inject)
 
+        if isinstance(terms, basestring):
+            terms = [ terms ]
+
         for term in terms:
             try:
                 self.reset()  # clear out things for this iteration