Subject: Update tempurl test

-updated the tempurl test module.
 added a test to check tempurl expiration.
 added assertions for the creation of the tempurl.
 moved hardcoded expiration times, etc to constants or they are being
 set in the setUpClass.
 added assertion messages to assertion where they were missing.
-added create_temp_container to the fixture.
-changed the method signature of create_temp_container in the fixture to set
 descriptor='' to default instead of check to see if it is None.
-pep8 fixes.
-removed unused import.

Change-Id: Ie54bce25a933aed981ca7f709fa6ef935238b0ad
Merge "Subject: Update tempurl test"