NetworkPkg: Fix possible infinite loop in HTTP msg body parser

NetworkPkg: Fix possible infinite loop in HTTP msg body parser

When an HTTP server sends a non-chunked body data with no
Content-Length header, the HttpParserMessageBody in DxeHttpLib
gets confused and never sets the Char pointer beyond the body start.
This causes "for" loop to never break because the condition of
"Char >= Body + BodyLength" is never satisfied.
Use BodyLength as the ContentLength for the parser when
ContentLength is absent in HTTP response headers.
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2941

Signed-off-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>