[SCSI] iscsi update: setup pool before using

>From andmike@us.ibm.com:

 Ensure that pool data is setup prior to calling mempool_create as it will
 call the the alloc function during create.

Signed-off-by: Mike Anderson <andmike@us.ibm.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Alex Aizman <itn780@yahoo.com>
Signed-off-by: Dmitry Yusupov <dmitry_yus@yahoo.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>