Actually checksum xattr values, not just names

We need to call lgetxattr() and not just llistxattr().

tests/t0005-nested-tree.sh

@@ -22,7 +22,7 @@ set -e
 
 . libtest.sh
 
-echo '1..3'
+echo '1..5'
 
 setup_test_repository2
 echo 'ok setup'
@@ -30,8 +30,10 @@ hacktree checkout $ht_repo HEAD $test_tmpdir/checkout2-head
 echo 'ok checkout cmd'
 cd $test_tmpdir/checkout2-head
 assert_has_file firstfile
+echo 'ok checkout firstfile'
 assert_has_file baz/cow
 assert_has_file baz/saucer
+echo 'ok checkout baz (2)'
 assert_has_file baz/deeper/ohyeah
 assert_has_file baz/another/y
 echo 'ok checkout verify exists'