Adding pre-stage log on api request

Currently jumpgate only logs api response with a post-stage logging
handler, it's a limitation for real-time debugging if the handling of
api request was blocked or needs a while to process, operator or
developer needs to know what api is hanlding there now and which api
request the log belongs to that the main handling logic logged, so this
change added a pre-stage logging for api request.
Merge pull request #154 from LiuZhiyan/adding-pre-log-on-request

Adding pre-stage log on api request