Also fix some tests that were not cleaning up after themselves, as
identified by the change to nonexistent_path.
* testsuite/util/testsuite_fs.h (nonexistent_path): Include name
of the source file containing the caller.
* testsuite/27_io/filesystem/iterators/directory_iterator.cc: Remove
directories created by test.
* testsuite/27_io/filesystem/iterators/recursive_directory_iterator.cc:
Likewise.
* testsuite/experimental/filesystem/iterators/directory_iterator.cc:
Likewise.
* testsuite/experimental/filesystem/iterators/
recursive_directory_iterator.cc: Likewise.
From-SVN: r267801
