[BUGFIX] Failing tests in Resource\Driver\LocalDriverTest on Windows

The test createdFilesAreEmpty depends on another test which returns a
mocked object. In the mock two returnValues for getIdentifier() and
getName() were set. But due to PHPUnit architecture mocked functions
belong to the test there were defined and cannot be shared. This is why
the mock has to be initialized within the test itself. The test only
works because on unix system you can open a folder which returns an
empty string.

Furthermore if you use any php function to get a folder path we have to
fix the containing backslashes.

Finally due to some errors we have to rewind any iterator of class
RecursiveIteratorIterator as otherwise a wrong index is returned.

Resolves: #50844
Releases: 6.2, 6.1, 6.0
Change-Id: I13f9efbd1618056fcd66220e3de5e12af79e4dc6
Reviewed-on: https://review.typo3.org/22904
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert