[SCSI] be2iscsi: Fix memory leak in control path of driver

In contorl path of the driver the task was mapped using
pci_map_single which was not unmapped when the completion
for the task had come.

Signed-off-by: John Soni Jose <sony.john-n@emulex.com>
Signed-off-by: Jayamohan Kallickal <jayamohan.kallickal@emulex.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>