Prevent admin role leak in context.elevated

context.elevated was creating a copy of the current context then adding
'admin' to the roles of that context. This should be a deepcopy, otherwise
'admin' is added to the original context too.

Change-Id: I8ab00c88a8e76a14fb9f4ae96dfdb5f018fc2d0f
Closes-bug: 1386932
Merge "Prevent admin role leak in context.elevated"