[IS-05-01] Check /staged information is unaffected by activation

[garethsb]

At a quick glance it looks like IS05Utils._check_perform_activation doesn't test if the transport_params etc. are kept in /staged after they are (approximately) copied to /active. Some similar kind of staging APIs reset the staging area to empty or default after activation, so although it is clear in IS-05 spec, it could be a natural mistake, which it may be good to check for in the test suite.