In our tests, we rely on the fact that when accessing a mongos as the `__system` user, we have to connect to the admin database. However, we don't account for this in the authorization manager code for acquire user.

```
StatusWith<UserHandle> AuthorizationManagerImpl::acquireUser(OperationContext* opCtx,
const UserName& userName){
if(userName == internalSecurity.user->getName())

```