Improve httpclient logs
Improve httpclient logs

Only dump requests/responses when the logging level is set to debug.

kensipe/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli