Add more tests for Swift Account Quota

2 new tests are added:

+ test that the admin is able to modify/remove a quota
  on a user's account

+ test that a user is not able to modify/remove a quota
  on its own account

Change-Id: I54cad8b244a26be8445fa4fe9ea63785aef4472a
Merge "Add more tests for Swift Account Quota"