Merge pull request #2586 from edx/max/fix-util-map

Small fixes

playbooks/library/util_map

@@ -17,7 +17,7 @@ options:
     description:
       - The input
     required: true
-  args
+  args:
     description:
       - Arguments to the function other than the input, varies by function.
 """
@@ -159,7 +159,7 @@ def main():
 
     arg_spec = dict(
         function=dict(required=True, type='str'),
-        input=dict(required=True, type='str'),
+        input=dict(required=True),
         args=dict(required=False, type='list'),
     )