SERVER-85475 moved the AuthorizationManager from being a decoration on ServiceContext, to a decoration on Service. The effect of this is that the AuthorizationManager's threads are no longer guaranteed to be joined before the invariant that the ServiceContext's Client set is empty is asserted in the ServiceContext destructor. (See BF-31901). This ticket proposes resetting the ServiceContext's unique_ptr<ServiceSet> member before the invariant is asserted.