Update functional tests for swift changes

It seems that a couple of changes to the store calls have slipped
through unnoticed:

* store.add() now returns a 4-tuple
* x-container-read and x-container-write headers use tenant:user rather
  than just tenant.

fixes bug 1236339

Change-Id: Ic5c311bcc2999e13203e0d3ad37bce5ac5f27e2d