etcdserver: close response body when getting cluster information

[magicwang-cn]

Fixes #5119

[heyitsanthony]

Why not just put a resp.Body.Close() before this line: https://github.com/coreos/etcd/blob/master/etcdserver/cluster_util.go#L76 ? Creating a closure seems like overkill...

Also the commit title should to be prefixed by the package name like etcdserver: close response body when getting cluster information

[magicwang-cn]

@heyitsanthony thanks for your review. i think it is more safer to use (defer) to clean unused resource, right? yeah. the commit should be clear

[heyitsanthony]

@magicwang-cn No, it's not safer. It's more complicated: semantically, lexically, and cyclomatically. The defer only buys a Close if ReadAll panics, but there's no recover, so it doesn't matter if the resource is closed anyway. Where's the additional safety, exactly?

[magicwang-cn]

yeah, you are right.:)

but there's no recover, so it doesn't matter if the resource is closed anyway

[heyitsanthony]

lgtm