VTKM_LOG_SCOPE no longer wraps a log around the given scope

The VTKM_LOG_SCOPE macro is supposed to create a starting log entry immediately and then make a second closing log entry once execution leaves the current scope. This is done by creating an object that creates the second closing log entry when it is destroyed (which happens when execution leaves the current scope). However, the implementation is broken in that it creates this object inside of a new scope that is left by the time the VTKM_LOG_SCOPE macro finishes. Thus, it immediately creates both the opening and closing log entries.

This feature seems to have broken in the creation of !2702 (merged).