MdeModulePkg ScsiBusDxe: Fix caller event may nerver be signaled

MdeModulePkg ScsiBusDxe: Fix caller event may nerver be signaled

For function ScsiExecuteSCSICommand(), when the 'Event' parameter is not
NULL but the target SCSI device does not support non-blocking I/O, it will
execute a blocking I/O operation instead.

However, after the SCSI operation is done, the 'Event' is not signaled to
inform the caller.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19217 6f19259b-4bc3-4df7-8a09-765794883524