[SCSI] libiscsi: fix iscsi pool leak

I am not sure what happened. It looks like we have always leaked
the q->queue that is allocated from the kfifo_init call. nab finally
noticed that we were leaking and this patch fixes it by adding a
kfree call to iscsi_pool_free. kfifo_free is not used per kfifo_init's
instructions to use kfree.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>