SfxMedium was creating a temporary file and copying the input file, when
CloseInStream_Impl was called from the destructor. Very very bad for
performance.

This is specifically fixing the performance of queryTypeByDescriptor
when called from a basic macro on a local test file.

This takes my test macro from 16.1s to 9s.

Change-Id: If52f8e0587c7b11666893f6cb79b3180d45cce43
Reviewed-on: https://gerrit.libreoffice.org/73375
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>