chore(tests): Try to fix file_directory_update test (#13636)

We've seen this test be flakier lately.

Rather than read all of `/tmp`, create a temporary directory to scope
the configuration watching to. Just a hunch that maybe using `/tmp` is
causing it to take a long time to read all of the files.

Also added some more debug statements.

Signed-off-by: Jesse Szwedko <jesse@szwedko.me>