* Refactor HTTP server to address bugs
* Remove unnecessary goroutine to start multiple TCP listeners.
* HTTP server waits for shutdown to maximum of Server.ShutdownTimeout
than per serverShutdownPoll.
* Handles new connection errors properly.
* Handles read and write timeout properly.
* Handles error on start of HTTP server properly by exiting minio
process.
Fixes#4494#4476 & fixed review comments
`principalId` i.e user identity is kept as AccessKey in
accordance with S3 spec.
Additionally responseElements{} are added starting with
`x-amz-request-id` is a hexadecimal of the event time itself in nanosecs.
`x-minio-origin-server` - points to the server generating the event.
Fixes#3556