Fix failure in manifest_test.go
Fix failure in manifest_test.go

TestWalkFS was failing as follows:
            manifest_test.go:163: Resource list difference
            manifest_test.go:171: Changed resource:
                            Expected: &continuity.symLink{resource:continuity.resource{paths:[]string{"/c/a-abssymlink"}, mode:0x80001ff, uid:"1001", gid:"100
1", xattrs:map[string][]uint8(nil)}, target:"/a"}
                            Actual:   &continuity.symLink{resource:continuity.resource{paths:[]string{"/c/a-abssymlink"}, mode:0x80001ff, uid:"1001", gid:"100
1", xattrs:map[string][]uint8{}}, target:"/tmp/continuity-test-356664233/a"}

Signed-off-by: Akihiro Suda <ea940da7e429af3d0d0c18296cabd0112a36bad5@lab.ntt.co.jp>

containerd/continuity,stevvooe/continuity,stevvooe/continuity