Let so_activex learn to work with Win32 errors and HRESULT properly

Previous code made ~no sense from error handling PoV. Closing registry
keys could be skipped because of prior errors; booleans were cast to
HRESULT to be checked later using SUCCEEDED macro.

Change-Id: I0735ab7e2f3b29682ab19adb0e96a581e997b8b5
Reviewed-on: https://gerrit.libreoffice.org/64425
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>