[SCSI] iscsi_tcp, ib_iser Enable module refcounting for iscsi host template

This prevents the iscsi modules from being unloaded while
there are active mounts from an iscsi target.

Signed-off-by: Olaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>