tests: fix cleanup after tests in t1509-root-worktree

During cleanup we do a simple 'rm /*' to remove leftover files
from previous tests. As 'rm' errors out when there is anything it
cannot delete and there are directories present at '/' it will
throw an error, causing the '&&' chain to fail.

Fix this by explicitly removing the files.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1509-root-worktree.sh

@@ -242,7 +242,7 @@ say "auto bare gitdir"
 # DESTROYYYYY!!!!!
 test_expect_success 'setup' '
 	rm -rf /refs /objects /info /hooks &&
-	rm /* &&
+	rm -f /expected /ls.expected /me /result &&
 	cd / &&
 	echo "Initialized empty Git repository in /" > expected &&
 	git init --bare > result &&