[SCSI] be2iscsi: WRB Initialization and Failure code path change

Removing code duplication during the WRB_Handle and WRB
initialization.
Added memory allocation failure handling code during WRB
initialization.

Signed-off-by: Jayamohan Kallickal <jayamohan.kallickal@emulex.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>