Added expiring objects test

* basic regression tests for X-Delete-At and X-Delete-After headers
  using standard, dynamic large, and static large objects
* added comments to the sleeps
* removed some unused imports
* added spaces after the # comments

Change-Id: I4907b80542bb2ef4bef6939e1d9027781692549e
Created parameterized versions of test.

Change-Id: I18ea037e975d78820b7c55c8d0cd4d481b336ca9
Merge "Added expiring objects test"
Merge "Created parameterized versions of test."