Apply mitigation to CimInstance disposal race condition

[cbnilrem]

This change disables automatic cleanup of base class memory, which appears to have been the cause of the race condition. The finalizer for the MI_Instance base class was running ahead of the CimInstance finalizer, causing the allocated block to be cleaned up before an explicit Delete() on the part of the CimInstance finalizer. This change switches to a Dispose() model for freeing MI_NativeObject instances, though it does not carry-through the usage to all appropriate places. As a result this change introduces a rather meaningful memory leak, but the leak is preferable to the crash in the near term as it was slowing down development.

[johnkord]

Signed off, as per our discussion, we'll address the new memory leak at a later time. Not seg-faulting is more important :)