[BUG] - HTTP request is not being closed properly

[optik-aper]

Describe the bug
The NopCloser doesn't actually close the request Body which annoys static analyzers and is probably going to create issues. Research whether the http library needs the response closed and what we can do to copy the response in a way that is useful to the new functionality exposing the request.

To Reproduce
Update DoWithContext's defer func in govultr.go to do something like this:

	defer func() {
		if err := res.Body.Close(); err != nil {
			fmt.Printf("Error: %v\n", err)
		}

		if bod, err := res.Body.Read(nil); err == nil {
			fmt.Printf("Body: %v\n", bod)
		}
	}()

It shouldn't be able to read the Body, but, the request is replaced by a NopCloser via:

	res.Body = io.NopCloser(bytes.NewBuffer(body))

The NopCloser actually just returns nil when you try to close it. https://cs.opensource.google/go/go/+/refs/tags/go1.20.6:src/io/io.go;l=678

This was added to allow us to return the request for use in the package, but, I'm concerned that it's going to leave connections open. Will need to test this further at some point.

Expected behavior
All http requests will close after completion

Desktop (please complete the following information where applicable:

• OS: ubuntu 22.04
• Language Version: go 1.20
• Browser: na
• Version: v3.1.0

Additional context

Golanci-lint calls bodyclose which tipped me off that something wasn't quite right here.

block_storage.go:121:33: response body must be closed (bodyclose)
	_, err = b.client.DoWithContext(ctx, req, nil)
	                               ^
block_storage.go:133:33: response body must be closed (bodyclose)
	_, err = b.client.DoWithContext(ctx, req, nil)
	                               ^
block_storage.go:171:33: response body must be closed (bodyclose)
	_, err = b.client.DoWithContext(ctx, req, nil)