add unittes for 'helm dep build' with --skip-refresh flag.
add unittes for 'helm dep build' with --skip-refresh flag.

Signed-off-by: yxxhero <16c1706a65ee90cb9f8059df2bda66bf3e935d9b@163.com>

adamreese/helm,bacongobbler/helm,adamreese/helm,helm/helm,helm/helm,bacongobbler/helm