rm unused sessions list.

This patch is last becuase I was not sure if this patchset was
going to be applied over the kmalloc2kzalloc one by JesS. If it
is then this patch will not apply and can be dropped for now. I will
resend later when things setttle down.
Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NAlex Aizman <itn780@yahoo.com>
Signed-off-by: NDmitry Yusupov <dmitry_yus@yahoo.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>