NetworkPkg: Fix HII related problem in HTTP boot driver.

NetworkPkg: Fix HII related problem in HTTP boot driver.

According to UEFI spec, HII_Config_Access.RouteConfig() should return success
if the required configuration has been processed. Current HTTP boot driver
may return error code in some situation, which failed the UEFI SCT test.
This patch fix this issue by removing the returned error status code and adding
extra check point in the Callback() function, which will pop up a message box
if user input an unsupported URI string.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Dong Eric <eric.dong@intel.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>