NetworkPkg:HttpDxe: Code changes to support HTTP PUT/POST operations

NetworkPkg:HttpDxe: Code changes to support HTTP PUT/POST operations

Code changes enables HttpDxe to handle PUT/POST operations.
EfiHttpRequest assumes "Request" and "HttpMsg->Headers" can
never be NULL. Also, HttpResponseWorker assumes HTTP Reponse
will contain headers. We could have response which could contain
only a string (HTTP 100 Continue) and no headers. Code changes
tries to do-away from these assumptions, which would enable
HttpDxe to support PUT/POST operations.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hegde, Nagaraj P nagaraj-p.hegde@hpe.com
Reviewed-By: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>