Set smoke/gate attributes for tests in "compute"

Change-Id: I3f6d496bd88b10f780b168caeb4b62d9138ae8e4
Implements: blueprint set-gate-attribute
Moved swift container cleanup to a class method.

The same piece of code was used in almost every tearDownClass method, moved it
into a separate method to remove code redundancy.

Change-Id: I173af3f46fc2f6771237ab29b472249b00a9ed2d
Merge "Set smoke/gate attributes for tests in "compute""
Merge "Moved swift container cleanup to a class method."