t1450: clean up sub-objects in duplicate-entry test

t1450: clean up sub-objects in duplicate-entry test

This test creates a multi-level set of trees, but its
cleanup routine only removes the top-level tree. After the
test finishes, the inner tree and the blob it points to
remain, making the inner tree dangling.

A later test ("cleaned up") verifies that we've removed any
cruft and "git fsck" output is clean. This passes only
because of a bug in git-fsck which fails to notice dangling
trees.

In preparation for fixing the bug, let's teach this earlier
test to clean up after itself correctly. We have to remove
the inner tree (and therefore the blob, too, which becomes
dangling after removing that tree).

Since the setup code happens inside a subshell, we can't
just set a variable for each object. However, we can stuff
all of the sha1s into the $T output variable, which is not
used for anything except cleanup.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>