Tempurl filename override fix

* added test for content-disposition INLINE
* added tests that expressly set content-disposition
* changed tests to reflect the change in what is set when
  content-disposition is generated
* changed dictionary['key'] to dictionary.get('key') where
  needed

Change-Id: I7dbc3b93c1aca172073b8f703b92c73f878b9897
Merge "Tempurl filename override fix"