Changing the args type for Pig jobs to a list

The args for a Pig job are now required to be a list rather
than a dict.  This change address that from the dashboard's perspective.

Partial-bug: #1269968

Change-Id: Ia4a30399686db4291e23efdbc9d7eea12a157a52
Merge "Changing the args type for Pig jobs to a list"