Change os.Getenv(HOME) to util.HomePath()

It is better to use util.HomePath() because it supports Windows, Linux,
and other platforms.

Signed-off-by: wangbicheng <wangbicheng@huawei.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Fix formatting in util/repository.go

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>