Run 002 and 003 in seperate temporary directories. (rt#86753)

both t/002Mult.t and t/003Dirs.t create t/data/tmp, and both attempt
to delete that path when its done.

This has a negative effect, because one will frequently terminate before
the other, and will delete all the files the other test relied upon.

So this patch does the smallest possible thing to resolve this,
creating the tempdirs suffixed by "_$$", which keeps everything clean,
and avoids frequent collisions.