Fixed storage container creating existing directory

Made storage container code check if the directory exists before
creating a new one over the top.

The previous behaviour was causing a crash on software created using the
PSM build (and perhaps others) of MonoGame.

Refer to issue #3061 for more information.
Moved directory exists change to the right function

Directory exists check now in CreateDirectoryAbsolute as per issue #3061
for pull request #3067.
Merge pull request #3067 from lordoaty/develop

Fixed storage container creating existing directory