MdeModulePkg/DxeCore: Fixed Interface returned by CoreOpenProtocol

MdeModulePkg/DxeCore: Fixed Interface returned by CoreOpenProtocol

Change since v4: Revise the patch based on V4 sent by Amit Kumar
1) Only return the corresponding protocol interface in *Interface
if the return status is EFI_SUCCESS or EFI_ALREADY_STARTED.
2) Interface is returned unmodified for all error conditions except
EFI_UNSUPPORTED and EFI_ALREADY_STARTED, NULL will be returned in
*Interface when EFI_UNSUPPORTED and Attributes is not
EFI_OPEN_PROTOCOL_TEST_PROTOCOL, the protocol interface will be
returned in *Interface when EFI_ALREADY_STARTED.

Change since v3:
1) Fixed issue when Attributes = EFI_OPEN_PROTOCOL_TEST_PROTOCOL
and Inteface = NULL case. [Reported by:star.zeng at intel.com]

Change Since v2:
1) Modified to use EFI_ERROR to get status code

Change since v1:
1) Fixed typo protocal to protocol
2) Fixed coding style

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Amit Kumar <amit.ak@samsung.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Gabriel Somlo <gsomlo@gmail.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Amit Kumar <amit.ak@samsung.com>
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Gabriel Somlo <gsomlo@gmail.com>