Bad workflow-steps check: has_required_fields

Many of the tabs on the Instance Creation screen don't show a "*"
despite having require fields.  This is due to faulty logic in determining
whether the workflow-step has require fields.  (Previously, only keys from
the contributes list were checked.)

Change-Id: Id609da27c51f8d4725683d7fd1534ead0c3bb984
Closes-Bug: 1252005
Merge "Bad workflow-steps check: has_required_fields"