Avoid crash in GDALDestructor() if it is called implicitely by OS mechanisms whereas GDALDestroy() has already been called (#5509)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27443 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx