Client does not use proxy settings while connecting to catalyst center

[becelot]

Currently, the client does ignore http proxy settings and times out, since I cannot reach catalyst center without the http proxy. Other tools and go client libraries work as expected, and are using the provided http proxy.

Reproduce

Set HTTP_PROXY and HTTPS_PROXY environment variable and use this library.

Expected behaviour

The client uses the proxy and fetches a response from CatalystCenter.

Actual behaviour

The client times out.

Further information

The problem is with the way that the InsecureSkipVerify flag is set. It accidentally overwrites the other default options available in tls.Transport (one of which is the Proxy setting, overwriting the default proxy setting inferred by go).

I tried the fix in my PR, and it works fine afterwards. I also recompiled the catalystcenter terraform provider with this fix (as it relies on this library), and terraform is also working fine afterwards.