Remove key-manager::api-storage privilege use in CKM tests

Remove key-manager::api-storage privilege use in CKM tests

Some CKM tests request the key-manager::api-storage privilege when
switching context to the user. However. this privilege was removed five
years ago (see commits 06d3064 and d5e32f8 in key-manager) and is no
longer required to use key-manager.

I have removed all calls responsible for requesting this privilege. This
also made it possible to only use the simplest ScopedAccessRequest
constructor and remove all other constructors.

Change-Id: I788e44f8e59575f80c8999b6b64eaefcc905fb75