generic: cleanup space after test in TESTDIR

generic: cleanup space after test in TESTDIR

A couple of tests leave behind large files or directory structures
when they complete, which leads to small TEST_DEVs running out of
space during other tests. Make those space hogs clean up after
themselves so that random tests don't fail with ENOSPC errors.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>