`wp_upload_dir()` has a (little-known?) side effect: if you call it, it will attempt to create an uploads directory for the current month. As such, `tearDown()` and cleanup routines have to be in sync with this behavior when deleting bogus directories used in unit tests.

Examples: if you clean up directories in a test, or a test fails before the directories are cleaned, or a test fails before the `'upload_path'` option is reset, the next call to `wp_upload_dir()` will recreate the directories you just tried to delete.

These changes ensure that `src/foo` and `/tmp/wp-unit-test` directories are deleted immediately after `wp_upload_dir()` is fired in the tests. 
 
Fixes #30513.


git-svn-id: https://develop.svn.wordpress.org/trunk@30658 602fd350-edb4-49c9-b593-d223f7449a82